Computable phenotype for diagnostic error: developing the data schema for application of symptom-disease pair analysis of diagnostic error (SPADE)

OBJECTIVES

Diagnostic errors are the leading cause of preventable harm in clinical practice. Implementable tools to quantify and target this problem are needed. To address this gap, we aimed to generalize the Symptom-Disease Pair Analysis of Diagnostic Error (SPADE) framework by developing its computable phenotype and then demonstrated how that schema could be applied in multiple clinical contexts.

METHODS

We created an information model for the SPADE processes, then mapped data fields from electronic health records (EHR) and claims data in use to that model to create the SPADE information model (intention) and the SPADE computable phenotype (extension). Later we validated the computable phenotype and tested it in four case studies in three different health systems to demonstrate its utility.

RESULTS

We mapped and tested the SPADE computable phenotype in three different sites using four different case studies. We showed that data fields to compute an SPADE base measure are fully available in the EHR Data Warehouse for extraction and can operationalize the SPADE framework from provider and/or insurer perspective, and they could be implemented on numerous health systems for future work in monitor misdiagnosis-related harms.

CONCLUSIONS

Data for the SPADE base measure is readily available in EHR and administrative claims. The method of data extraction is potentially universally applicable, and the data extracted is conveniently available within a network system. Further study is needed to validate the computable phenotype across different settings with different data infrastructures.

Risk of Major Adverse Cardiovascular Events After Emergency Department Visits for Hypertensive Urgency

BACKGROUND

Chronic hypertension is an established long-term risk factor for major adverse cardiovascular events (MACEs). However, little is known about short-term MACE risk after hypertensive urgency, defined as an episode of acute severe hypertension without evidence of target-organ damage. We sought to evaluate the short-term risk of MACE after an emergency department (ED) visit for hypertensive urgency resulting in discharge to home.

METHODS

We performed a case-crossover study using deidentified administrative claims data. Our case periods were 1-week intervals from 0 to 12 weeks before hospitalization for MACE. We compared ED visits for hypertensive urgency during these case periods versus equivalent control periods 1 year earlier. Hypertensive urgency and MACE components were all ascertained using previously validated International Classification of Diseases, Tenth Revision Clinical Modification codes. We used McNemar test for matched data to calculate risk ratios.

RESULTS

Among 2 225 722 patients with MACE, 1 893 401 (85.1%) had a prior diagnosis of hypertension. There were 4644 (0.2%) patients who had at least 1 ED visit for hypertensive urgency during the 12 weeks preceding their MACE hospitalization. An ED visit for hypertensive urgency was significantly more common in the first week before MACE compared with the same chronological week 1 year earlier (risk ratio, 3.5 [95% CI, 2.9-4.2]). The association between hypertensive urgency and MACE decreased in magnitude with increasing temporal distance from MACE and was no longer significant by 11 weeks before MACE (risk ratio, 1.2 [95% CI, 0.99-1.6]).

CONCLUSIONS

ED visits for hypertensive urgency were associated with a substantially increased short-term risk of subsequent MACE.

Cost-Effectiveness of Increased Use of Dual Antiplatelet Therapy After High-Risk Transient Ischemic Attack or Minor Stroke

BACKGROUND

Rates of dual antiplatelet therapy (DAPT) after high-risk transient ischemic attack or minor ischemic stroke (TIAMIS) are suboptimal. We performed a cost-effectiveness analysis to characterize the parameters of a quality improvement (QI) intervention designed to increase DAPT use after TIAMIS.

METHODS AND RESULTS

We constructed a decision tree model that compared current national rates of DAPT use after TIAMIS with rates after implementing a theoretical QI intervention designed to increase appropriate DAPT use. The base case assumed that a QI intervention increased the rate of DAPT use to 65% from 45%. Costs (payer and societal) and outcomes (stroke, myocardial infarction, major bleed, or death) were modeled using a lifetime horizon. An incremental cost-effectiveness ratio <$100 000 per quality-adjusted life year was considered cost-effective. Deterministic and probabilistic sensitivity analyses were performed. From the payer perspective, a QI intervention was associated with $9657 in lifetime cost savings and 0.18 more quality-adjusted life years compared with current national treatment rates. A QI intervention was cost-effective in 73% of probabilistic sensitivity analysis iterations. Results were similar from the societal perspective. The maximum acceptable, initial, 1-time payer cost of a QI intervention was $28 032 per patient. A QI intervention that increased DAPT use to at least 51% was cost-effective in the base case.

CONCLUSIONS

Increasing DAPT use after TIAMIS with a QI intervention is cost-effective over a wide range of costs and proportion of patients with TIAMIS treated with DAPT after implementation of a QI intervention. Our results support the development of future interventions focused on increasing DAPT use after TIAMIS.

Association of Assisted Reproductive Technology and Stroke During Hospitalization for Delivery in the United States

Background: Infertility treatment with assisted reproductive technologies (ART) has been associated with adverse vascular events in some, but not all previous studies. Endothelial damage, prothrombotic factor release, and a higher prevalence of cardiovascular risk factors in those receiving ART have been invoked to explain this association. We sought to explore the relationship between ART and stroke risk using population-level data. Methods: We conducted a retrospective cohort study using data from the National Inpatient Sample (NIS) registry from 2015-2020, including all delivery hospitalizations for patients aged 15-55 years. The study exposure was use of ART. The primary endpoint was any stroke defined as ischemic stroke (IS), subarachnoid hemorrhage (SAH), intracerebral hemorrhage (ICH), or cerebral venous thrombosis (CVT) during index delivery hospitalization. Individual stroke subtypes (IS, SAH, ICH, and CVT) were evaluated as secondary endpoints. Standard International Classification of Diseases, Tenth Revision, Clinical Modification (ICD-10-CM) algorithms were used to define study exposure, comorbidities, and prespecified endpoints. In addition to reporting population-level estimates, propensity score (PS) adjustment by inverse probability weighting (IPW) was used to mimic the effects of randomization by balancing baseline clinical characteristics associated with stroke between ART and non-ART users. Results: Among 19,123,125 delivery hospitalizations identified, patients with prior ART (n = 202,815, 1.1%) experienced significantly higher rates of any stroke (27.1/100,000 vs. 9.1/100,000), IS (9.9/100,000 vs. 3.3/100,000), SAH (7.4/100,000 vs. 1.6/100,000), ICH (7.4/100,000 vs. 2.0/100,000), and CVT (7.4/100,000 vs. 2.7/100,000) in comparison to non-ART users (all p < 0.001 for all unadjusted comparisons). Following IPW analysis, ART was associated with increased odds of any stroke (aOR 2.14 [95% CI 2.02-2.26]; p < 0.001). Conclusion: Using population-level data among patients hospitalized for delivery in the United States, we found an association between ART and stroke after adjustment for measured confounders.

Delayed Diagnosis in Cerebral Venous Thrombosis: Associated Factors and Clinical Outcomes

Background Identifying factors associated with delayed diagnosis of cerebral venous thrombosis (CVT) can inform future strategies for early detection. Methods and Results We conducted a retrospective cohort study including all participants from ACTION-CVT (Anticoagulation in the Treatment of Cerebral Venous Thrombosis) study who had dates of neurologic symptom onset and CVT diagnosis available. Delayed diagnosis was defined as CVT diagnosis occurring in the fourth (final) quartile of days from symptom onset. The primary study outcome was modified Rankin Scale score of ≤1 at 90 days; secondary outcomes included partial/complete CVT recanalization on last available imaging and modified Rankin Scale score of ≤2. Logistic regression analyses were used to identify independent variables associated with delayed diagnosis and to assess the association of delayed diagnosis and outcomes. A total of 935 patients were included in our study. Median time from symptom onset to diagnosis was 4 days (interquartile range, 1-10 days). Delayed CVT diagnosis (time to diagnosis >10 days) occurred in 212 patients (23%). Isolated headache (adjusted odds ratio [aOR], 2.36 [95% CI, 1.50-3.73]; P<0.001), older age (aOR by 1 year, 1.02 [95% CI, 1.004-1.03]; P=0.01), and papilledema (aOR, 2.00 [95% CI, 1.03-3.89]; P=0.04) were associated with diagnostic delay, whereas higher National Institutes of Health Stroke Scale score was inversely associated with diagnostic delay (aOR by 1 point, 0.95 [95% CI, 0.89-1.00]; P=0.049). Delayed diagnosis was not associated with modified Rankin Scale score of ≤1 at 90 days (aOR, 1.08 [95% CI, 0.60-1.96]; P=0.79). Conclusions In a large multicenter cohort, a quarter of included patients with CVT were diagnosed >10 days after symptom onset. Delayed CVT diagnosis was associated with the symptom of isolated headache and was not associated with adverse clinical outcomes.

Misdiagnosis of Posterior Reversible Encephalopathy Syndrome and Reversible Cerebral Vasoconstriction Syndrome in the Emergency Department

Background Cerebrovascular dysregulation syndromes, posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS), are challenging to diagnose because they are rare and require advanced neuroimaging for confirmation. We sought to estimate PRES/RCVS misdiagnosis in the emergency department and its associated factors. Methods and Results We conducted a retrospective cohort study of PRES/RCVS patients using administrative claims data from 11 states (2016-2018). We defined patients with a probable PRES/RCVS misdiagnosis as those with an emergency department visit for a neurological symptom resulting in discharge to home that occurred ≤14 days before PRES/RCVS hospitalization. Proportions of patients with probable misdiagnosis were calculated, characteristics of patients with and without probable misdiagnosis were compared, and regression analyses adjusted for demographics and comorbidities were performed to identify factors affecting probable misdiagnosis. We identified 4633 patients with PRES/RCVS. A total of 210 patients (4.53% [95% CI, 3.97-5.17]) had a probable preceding emergency department misdiagnosis; these patients were younger (mean age, 48 versus 54 years; P<0.001) and more often female (80.4% versus 69.3%; P<0.001). Misdiagnosed patients had fewer vascular risk factors except prior stroke (36.3% versus 24.2%; P<0.001) and more often had comorbid headache (84% versus 21.4%; P<0.001) and substance use disorder (48.8% versus 37.9%; P<0.001). Facility-level factors associated with probable misdiagnosis included smaller facility, lacking a residency program (62.2% versus 73.7%; P<0.001), and not having on-site neurological services (75.7% versus 84.3%; P<0.001). Probable misdiagnosis was not associated with higher likelihood of stroke or subarachnoid hemorrhage during PRES/RCVS hospitalization. Conclusions Probable emergency department misdiagnosis occurred in ≈1 of every 20 patients with PRES/RCVS in a large, multistate cohort.

Optimizing measurement of misdiagnosis-related harms using symptom-disease pair analysis of diagnostic error (SPADE): comparison groups to maximize SPADE validity

Diagnostic errors in medicine represent a significant public health problem but continue to be challenging to measure accurately, reliably, and efficiently. The recently developed Symptom-Disease Pair Analysis of Diagnostic Error (SPADE) approach measures misdiagnosis related harms using electronic health records or administrative claims data. The approach is clinically valid, methodologically sound, statistically robust, and operationally viable without the requirement for manual chart review. This paper clarifies aspects of the SPADE analysis to assure that researchers apply this method to yield valid results with a particular emphasis on defining appropriate comparator groups and analytical strategies for balancing differences between these groups. We discuss four distinct types of comparators (intra-group and inter-group for both look-back and look-forward analyses), detailing the rationale for choosing one over the other and inferences that can be drawn from these comparative analyses. Our aim is that these additional analytical practices will improve the validity of SPADE and related approaches to quantify diagnostic error in medicine.

Comparing the effects of four common drug classes on the progression of mild cognitive impairment to dementia using electronic health records

The objective of this study was to investigate the potential association between the use of four frequently prescribed drug classes, namely antihypertensive drugs, statins, selective serotonin reuptake inhibitors, and proton-pump inhibitors, and the likelihood of disease progression from mild cognitive impairment (MCI) to dementia using electronic health records (EHRs). We conducted a retrospective cohort study using observational EHRs from a cohort of approximately 2 million patients seen at a large, multi-specialty urban academic medical center in New York City, USA between 2008 and 2020 to automatically emulate the randomized controlled trials. For each drug class, two exposure groups were identified based on the prescription orders documented in the EHRs following their MCI diagnosis. During follow-up, we measured drug efficacy based on the incidence of dementia and estimated the average treatment effect (ATE) of various drugs. To ensure the robustness of our findings, we confirmed the ATE estimates via bootstrapping and presented associated 95% confidence intervals (CIs). Our analysis identified 14,269 MCI patients, among whom 2501 (17.5%) progressed to dementia. Using average treatment estimation and bootstrapping confirmation, we observed that drugs including rosuvastatin (ATE = - 0.0140 [- 0.0191, - 0.0088], p value < 0.001), citalopram (ATE = - 0.1128 [- 0.125, - 0.1005], p value < 0.001), escitalopram (ATE = - 0.0560 [- 0.0615, - 0.0506], p value < 0.001), and omeprazole (ATE = - 0.0201 [- 0.0299, - 0.0103], p value < 0.001) have a statistically significant association in slowing the progression from MCI to dementia. The findings from this study support the commonly prescribed drugs in altering the progression from MCI to dementia and warrant further investigation.

Diagnosis and Treatment of Cerebral Venous Thrombosis

OBJECTIVE

Cerebral venous thrombosis (CVT), thrombosis of the dural sinus, cerebral veins, or both, is a rare cerebrovascular disease. Although mortality rates after CVT have declined over time, this condition can result in devastating neurologic outcomes. This article reviews the latest literature regarding CVT epidemiology, details new factors associated with the development of CVT, and describes advances in CVT treatment. It also contains a discussion of future directions in the field, including novel diagnostic imaging modalities, and potential strategies to reduce the risks associated with CVT.

LATEST DEVELOPMENTS

The incidence of CVT may be as high as 2 per 100,000 adults per year. It remains a difficult condition to diagnose given its variable clinical manifestations and the necessity of neuroimaging for confirmation. The COVID-19 pandemic has revealed a novel CVT trigger, vaccine-induced immune thrombotic thrombocytopenia (VITT), as well as an association between COVID-19 infection and CVT. Although VITT is a very rare event, timely diagnosis and treatment of CVT due to VITT likely improves patient outcomes. Direct oral anticoagulants are currently being used to treat CVT and emerging data suggest that these agents are as safe and effective as vitamin K antagonists. The role of endovascular therapy to treat CVT, despite a recent clinical trial, remains unproven.

ESSENTIAL POINTS

The incidence of CVT has increased, outcomes have improved, and the use of direct oral anticoagulants to treat CVT represents an important advance in the clinical care of these patients. Rates of CVT as a complication of COVID-19 vaccines using adenoviral vectors are very low (<5 per million vaccine doses administered), with the benefits of COVID-19 vaccination far outweighing the risks.

Cost-Effectiveness of Smoking Cessation Interventions in Patients With Ischemic Stroke and Transient Ischemic Attack

BACKGROUND

Smoking cessation rates after stroke and transient ischemic attack are suboptimal, and smoking cessation interventions are underutilized. We performed a cost-effectiveness analysis of smoking cessation interventions in this population.

METHODS

We constructed a decision tree and used Markov models that aimed to assess the cost-effectiveness of varenicline, any pharmacotherapy with intensive counseling, and monetary incentives, compared with brief counseling alone in the secondary stroke prevention setting. Payer and societal costs of interventions and outcomes were modeled. The outcomes were recurrent stroke, myocardial infarction, and death using a lifetime horizon. Estimates and variance for the base case (35% cessation), costs and effectiveness of interventions, and outcome rates were imputed from the stroke literature. We calculated incremental cost-effectiveness ratios and incremental net monetary benefits. An intervention was considered cost-effective if the incremental cost-effectiveness ratio was less than the willingness-to-pay threshold of $100 000 per quality-adjusted life-year (QALY) or when the incremental net monetary benefit was positive. Probabilistic Monte Carlo simulations modeled the impact of parameter uncertainty.

RESULTS

From the payer perspective, varenicline and pharmacotherapy with intensive counseling were associated with more QALYs (0.67 and 1.00, respectively) at less total lifetime costs compared with brief counseling alone. Monetary incentives were associated with 0.71 more QALYs at an additional cost of $120 compared with brief counseling alone, yielding an incremental cost-effectiveness ratio of $168/QALY. From the societal perspective, all 3 interventions provided more QALYs at less total costs compared with brief counseling alone. In 10 000 Monte Carlo simulations, all 3 smoking cessation interventions were cost-effective in >89% of runs.

CONCLUSIONS

For secondary stroke prevention, it is cost-effective and potentially cost-saving to deliver smoking cessation therapy beyond brief counseling alone.

Risk assessment of the acute stroke diagnostic process using failure modes, effects, and criticality analysis

INTRODUCTION

To date, many emergency department (ED)-based quality improvement studies and interventions for acute stroke patients have focused on expediting time-sensitive treatments, particularly reducing door-to-needle time. However, prior to treatment, a diagnosis of stroke must be reached. The ED-based stroke diagnostic process has been understudied despite its importance in assuring high-quality and safe care.

METHODS

We used a learning collaborative to conduct a failure modes, effects, and criticality analysis (FMECA) of the acute stroke diagnostic process at three health systems in Chicago, IL. Our FMECA was designed to prospectively identify, characterize, and rank order failures in the systems and processes of care that offer opportunities for redesign to improve stroke diagnostic accuracy. Multidisciplinary teams involved in stroke care at five different sites participated in moderated sessions to create an acute stroke diagnostic process map as well as identify failures and existing safeguards. For each failure, a risk priority number and criticality score were calculated. Failures were then ranked, with the highest scores representing the most critical failures to be targeted for redesign.

RESULTS

A total of 28 steps were identified in the acute stroke diagnostic process. Iterative steps in the process include information gathering, clinical examination, interpretation of diagnostic test results, and reassessment. We found that failure to use existing screening scales to identify patients with large-vessel occlusions early on in their ED course ranked highest. Failure to obtain an accurate history of the index event, failure to suspect acute stroke in triage, and failure to use established stroke screening tools at ED arrival to identify potential stroke patients were also highly ranked.

CONCLUSIONS

Our study results highlight the critical importance of upstream steps in the acute stroke diagnostic process, particularly the use of existing tools to identify stroke patients who may be eligible for time-sensitive treatments.

Validation of the International Classification of Diseases, Tenth Revision Code for the National Institutes of Health Stroke Scale Score

BACKGROUND

Administrative data can be useful for stroke research but have historically lacked data on stroke severity. Hospitals increasingly report the National Institutes of Health Stroke Scale (NIHSS) score using an International Classification of Diseases, Tenth Revision (ICD-10) diagnosis code, but this code's validity remains unclear.

METHODS

We examined the concordance of ICD-10 NIHSS scores versus NIHSS scores recorded in CAESAR (Cornell Acute Stroke Academic Registry). We included all patients with acute ischemic stroke from October 1, 2015, when US hospitals transitioned to ICD-10, through 2018, the latest year in our registry. The NIHSS score (range, 0-42) recorded in our registry served as the reference gold standard. ICD-10 NIHSS scores were derived from hospital discharge diagnosis code R29.7xx, with the latter 2 digits representing the NIHSS score. Multiple logistic regression was used to explore factors associated with availability of ICD-10 NIHSS scores. We used ANOVA to examine the proportion of variation (R2) in the true (registry) NIHSS score that was explained by the ICD-10 NIHSS score.

RESULTS

Among 1357 patients, 395 (29.1%) had an ICD-10 NIHSS score recorded. This proportion increased from 0% in 2015 to 46.5% in 2018. In a logistic regression model, only higher registry NIHSS score (odds ratio per point, 1.05 [95% CI, 1.03-1.07]) and cardioembolic stroke (odds ratio, 1.4 [95% CI, 1.0-2.0]) were associated with availability of the ICD-10 NIHSS score. In an ANOVA model, the ICD-10 NIHSS score explained almost all the variation in the registry NIHSS score (R2=0.88). Fewer than 10% of patients had a large discordance (≥4 points) between their ICD-10 and registry NIHSS scores.

CONCLUSIONS

When present, ICD-10 codes representing NIHSS scores had excellent agreement with NIHSS scores recorded in our stroke registry. However, ICD-10 NIHSS scores were often missing, especially in less severe strokes, limiting the reliability of these codes for risk adjustment.

Long-term risk of seizure after posterior reversible encephalopathy syndrome

OBJECTIVE

Patients with posterior reversible encephalopathy syndrome (PRES) can develop seizures during the acute phase. We sought to determine the long-term risk of seizure after PRES.

METHODS

We performed a retrospective cohort study using statewide all-payer claims data from 2016-2018 from nonfederal hospitals in 11 US states. Adults admitted with PRES were compared to adults admitted with stroke, an acute cerebrovascular disorder associated with long-term risk of seizure. The primary outcome was seizure diagnosed during an emergency room visit or hospital admission after the index hospitalization. The secondary outcome was status epilepticus. Diagnoses were determined using previously validated ICD-10-CM codes. Patients with seizure diagnoses before or during the index admission were excluded. We used Cox regression to evaluate the association of PRES with seizure, adjusting for demographics and potential confounders.

RESULTS

We identified 2095 patients hospitalized with PRES and 341,809 with stroke. Median follow-up was 0.9 years (IQR, 0.3-1.7) in the PRES group and 1.0 years (IQR, 0.4-1.8) in the stroke group. Crude seizure incidence per 100 person-years was 9.5 after PRES and 2.5 after stroke. After adjustment for demographics and comorbidities, patients with PRES had a higher risk of seizure than patients with stroke (HR, 2.9; 95% CI, 2.6-3.4). Results were unchanged in a sensitivity analysis that applied a two-week washout period to mitigate detection bias. A similar relationship was observed for the secondary outcome of status epilepticus.

INTERPRETATION

PRES was associated with an increased long-term risk of subsequent acute care utilization for seizure compared to stroke.

The International Classification of Diseases, 10 th Edition, Clinical Modification (ICD-10-CM) Code I16.0 Accurately Identifies Patients with Hypertensive Urgency

Objective

Hypertensive urgency, defined as acutely elevated BP without target organ damage, is associated with an increased risk of adverse cardiovascular events and accounts for a substantial proportion of national emergency department (ED) visits. To advance research in this space, we sought to validate the new ICD-10-CM diagnostic code for hypertensive urgency within a single healthcare system.

Methods

We performed a retrospective chart-review study of ED encounters at Weill Cornell Medicine from 2016 â€" 2021. We randomly selected 25 encounters with the ICD-10-CM code I16.0 as the primary discharge diagnosis and 25 encounters with primary ICD-10-CM discharge diagnosis codes for benign headache disorders. A single board-certified vascular neurologist reviewed all 50 encounters while blinded to the assigned ICD-10-CM codes to identify cases of hypertensive urgency. We calculated the sensitivity, specificity, and positive predictive values of the ICD-10-CM code I16.0 with 95% confidence intervals (CI).

Results

Out of 50 randomly selected ED encounters, 24 were adjudicated as hypertensive urgency. All encounters adjudicated as hypertensive urgency had been assigned the ICD-10-CM discharge diagnosis code of I16.0. All 25 of the encounters adjudicated as headache were assigned an ICD-10-CM discharge diagnosis code for a benign headache disorder. The ICD-10-CM code for hypertensive urgency, I16.0, was thus found to have a sensitivity of 100% (95% CI: 86-100%), specificity of 96% (95% CI: 80-100%), and positive predictive value of 96% (95% CI: 78-99%).

Conclusion

We found that the new ICD-10-CM code for hypertensive urgency, I16.0, can reliably identify patients with this condition.

Abstract 34: Liver Fibrosis, Apolipoprotein E, And Hemorrhagic Stroke Risk: A Cohort Analysis

Introduction: Cirrhosis is associated with an increased risk of hemorrhagic stroke (HS). Liver fibrosis, typically a silent condition, is antecedent to cirrhosis. We hypothesized that liver fibrosis is associated with an increased risk of HS. Further, because apolipoprotein E2 (ApoE2) and E4 (ApoE4) are associated with HS, and because liver-derived peripheral ApoE4 may disrupt endothelial integrity, we evaluated for effect modification by these isoforms.

Methods: We performed a cohort analysis using the UK Biobank Study, which prospectively enrolled adults in 2007, with continuous follow-up. We excluded participants with prevalent HS or thrombocytopenia. Liver fibrosis was defined using the validated Fibrosis-4 score. The primary outcome, incident HS (intracerebral or subarachnoid hemorrhage), was captured in UK Biobank based on hospitalization and death registry data. We used Cox proportional hazards models to evaluate the association of liver fibrosis with HS while adjusting for HS risk factors (demographics, systolic blood pressure, hemoglobin A1c, total cholesterol, BMI, tobacco and alcohol use, antithrombotic use). Effect modification by ApoE2 and ApoE4 were evaluated using interaction terms and stratified analyses.

Results: Among 453,251 included participants, the mean age was 57 years and 54% were women. Approximately 2% had liver fibrosis, 16% used antithrombotic agents, 29% were ApoE4 carriers, and 15% were ApoE2 carriers. In adjusted Cox models, liver fibrosis was associated with an increased risk of HS (HR, 2.17; 95% CI, 1.51-3.12) (Figure). This relationship appeared stronger in ApoE4 homozygotes (HR, 8.27; 95% CI, 2.30-29.73) than in others (HR, 2.18; 95% CI, 1.47-3.24) (P=0.05, interaction). ApoE4 carrier status, ApoE2 carrier status, and ApoE2 homozygosity did not modify this relationship (P>0.20, interactions).

Conclusions: Liver fibrosis was associated with an increased risk of HS, possibly more so in ApoE4 homozygous persons.

Abstract WP70: Emergency Department Visits For Hypertensive Urgency And Risk Of Subsequent Stroke

Introduction: Chronic hypertension is an established long-term risk factor for stroke. However, little is known about short-term stroke risk after an episode of acute severe hypertension without evidence of target organ damage (i.e., hypertensive urgency [HU]). We evaluated the short-term risk of stroke after an ED visit with HU resulting in discharge home (treat-and-release).

Methods: We performed a case-crossover study using deidentified administrative claims from all nonfederal EDs and hospitals across 11 states. The study cohort comprised patients diagnosed with any stroke (ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage), defined using validated ICD-10 codes, between 2016-2018. We tabulated and compared incident ED visits for HU during case periods (2-week intervals from 0-24 weeks before the index stroke) to control periods (equivalent time periods exactly 1 year earlier). ED visits with HU were ascertained using the ICD-10 code I16.0, which we validated through detailed chart review of 50 patients at our center resulting in a code sensitivity and specificity of 100% and 96%, respectively. We used McNemar’s test for matched data to calculate risk ratios (RRs) for an ED HU visit occurring before stroke.

Results: Among 45,063 patients with stroke, 22,417 (50%) were female and 37,577 (83%) had a prior diagnosis of hypertension. There were 201 patients with stroke who had at least one ED visit for HU during the preceding 24 weeks. An ED visit for HU was significantly more common in the 2 weeks before stroke compared to the 2-week control period 1 year earlier (RR, 5.1; 95% CI, 2.4-12.7; p<0.0001). The association between stroke and preceding ED visit for HU decreased in magnitude with increasing temporal distance from stroke and was no longer significant by the 7-8 week period before stroke (Figure 1).

Conclusion: Treat-and-release ED visits for HU are associated with a significantly increased short-term risk of stroke.

Prevalence of neurological complaints among emergency department patients with severe hypertension

OBJECTIVE

Severe hypertension can accompany neurological symptoms without obvious signs of target organ damage. However, acute cerebrovascular events can also be a cause and consequence of severe hypertension. We therefore use US population-level data to determine prevalence and clinical characteristics of patients with severe hypertension and neurological complaints.

METHODS

We used nationally representative data from the National Hospital Ambulatory Medical Care Survey (NHAMCS) collected in 2016-2019 to identify adult ED patients with severely elevated blood pressure (BP) defined as systolic BP ≥ 180 mmHg and/or diastolic BP ≥120 mmHg. We used ED reason for visit data fields to define neurological complaints and used diagnosis data fields to define acute target organ damage. We applied survey visit weights to obtain national estimates.

RESULTS

Based on 5083 observations, an estimated 40.4 million patients (95% CI: 37.5-43.0 million) in EDs nationwide from 2016 to 2019 had severe hypertension, equating to 6.1% (95% CI: 5.7-6.5%) of all ED visits. Only 2.8% (95% CI: 2.0-3.9%) of ED patients with severe hypertension were diagnosed with acute cerebrovascular disease; hypertensive urgency was diagnosed in 92.0% (95% CI: 90.3-93.4%). Neurological complaints were frequent in both patients with (75.6%) and without (19.9%) cerebrovascular diagnoses. Hypertensive urgency patients with neurological complaints were more often older, female, had prior stroke/TIA, and had neuroimaging than patients without these complaints. Non-migraine headache and vertigo were the most common neurological complaints recorded.

CONCLUSION

In a nationally representative survey, one-in-sixteen ED patients had severely elevated BP and one-fifth of those patients had neurological complaints.

Abstract TMP55: Factors Associated With Delayed Diagnosis Of Cerebral Venous Thrombosis: Secondary Analysis Of ACTION-CVT Study

Introduction: Few clinical features have been associated with delayed diagnosis of cerebral venous thrombosis with variable impact of delay on patient outcomes. We therefore sought to use the data from a recent, multicenter study ACTION-CVT (Anticoagulation in the Treatment of CVT) to identify factors associated with delayed CVT diagnosis and evaluate the effect of delay on functional outcome.

Methods: All ACTION-CVT patients with available data on date of neurological symptom onset and date of CVT diagnosis were included. Delayed diagnosis of CVT was defined as diagnosis occurring in the fourth (final) quartile of days from symptom onset. We also report the proportion of patients who were discharged from hospital or ED within 3 months prior to index CVT admission for any neurological symptom without being diagnosed with CVT. The primary study outcome was an excellent functional outcome at 90 days defined as modified Rankin Scale (mRS) ≤1. Secondary outcome was partial or complete CVT recanalization on last available venous imaging. Chi-squared and Student’s t-tests were used to identify variables associated with delayed diagnosis. Logistic regression was used to identify independent predictors of delayed diagnosis in CVT as well as the association of delay with outcomes.

Results: We included 935 CVT patients in our analysis. Median time from symptom onset to diagnosis was 4 days (IQR: 1-10). Delayed CVT diagnosis occurred in 212 (23%) patients (median time to diagnosis >10 days). Out of 212 patients with delayed CVT diagnosis, 64 (30.2%) patients were discharged from hospital/ED in the 3 months prior to their index CVT admission. Headache symptoms were a predictor of delayed diagnosis (OR: 2.36 [1.26-4.42]; p<0.01), and seizure was inversely related to delayed diagnosis (0.39 [0.21-0.74]; p=0.001). Delayed diagnosis was not associated with mRS ≤1 at 90 days (OR 0.83 [95% CI: 0.42-1.64]; p=0.58) or venous recanalization (OR 1.78 [95% CI 0.79-3.99]; p=0.16).

Conclusion: In a large, multicenter cohort we found that CVT patients presenting with headache were at increased risk of delayed diagnosis, however, delayed diagnosis was not associated with adverse outcomes. CVT diagnosis should be considered in patients presenting with a new headache.

Abstract WP197: The Association Between Atherosclerotic Disease And Cervical Artery Dissection In A Large Population-based Cohort Of Older People

Introduction: While well-established risk factors for cervical artery dissection include trauma and connective tissue disorders, many cases are considered “spontaneous.” Although the incidence of cervical artery dissection is greatest in the young, the prevalence increases with age, suggesting a potential role of vascular disease. In this study, we hypothesized that atherosclerosis may be a risk factor for cervical artery dissection.

Methods: We performed a retrospective cohort study using administrative claims data from a 5% sample of Medicare beneficiaries between 2008 and 2018. The exposures of interest were vascular risk factors potentially associated with atherosclerosis including coronary artery disease, hyperlipidemia, hypertension, diabetes mellitus, heart failure, chronic kidney disease, chronic obstructive pulmonary disease, valvular heart disease, atrial fibrillation, tobacco use, and alcohol abuse. The primary outcome was a new diagnosis of cervical artery dissection. Marginal structural Cox models were used to characterize the association between the exposures and outcomes, adjusted for time-dependent confounding, age, sex, race/ethnicity, and prior stroke.

Results: Among 2,256,826 eligible Medicare beneficiaries, 1,527 (0.07%) developed cervical artery dissection, with a mean age of 70.8, compared to 71.5 in those without cervical artery dissection. The following exposures were found to be significantly associated with the development of cervical artery dissection: coronary artery disease (1.81 [1.63-2.01]), hyperlipidemia (1.84 [1.61-2.11]), hypertension (2.04 [1.76-2.37]), diabetes mellitus (1.34 [1.21-1.49]), heart failure (1.44 [1.25-1.67]), chronic kidney disease (1.38 [1.20-1.59]), chronic obstructive pulmonary disease (1.3 [1.16-1.46]), valvular heart disease (1.81 [1.60-2.04]), atrial fibrillation (HR 1.75 [95% CI 1.54-1.98]), tobacco use (1.84 [1.57-2.15]), and alcohol abuse (1.84 [1.56-2.16]).

Conclusion: In a large population-based cohort of older people, atherosclerotic risk factors were associated with subsequent cervical artery dissection. Further studies exploring the role of atherosclerosis in the development of cervical artery dissection are required.

Prevalence of Neurological Complaints in US Emergency Departments, 2016-2019

This study uses data from the National Hospital Ambulatory Medical Care Survey to analyze adults with a neurological complaint as their reason for an emergency department visit.

Abstract WP77: Cost-effectiveness Analysis Of Increasing Dual Antiplatelet Therapy Treatment After High-risk Transient Ischemic Attack Or Minor Ischemic Stroke

Background: Use of guideline recommended dual antiplatelet therapy (DAPT) after high-risk TIA or minor ischemic stroke is suboptimal. We performed a cost-effectiveness analysis of current DAPT treatment patterns and modeled optimal parameters for future healthcare delivery quality improvement (QI) interventions designed to increase DAPT use.

Methods: We constructed two decision tree models. Our first model compared DAPT (90 days of aspirin and clopidogrel) to aspirin alone at current national treatment rates (45% of eligible patients receive DAPT). Our second model compared current DAPT treatment patterns to a theoretical QI intervention that increases DAPT use at an initial cost of $20,000 per institution, in keeping with costs of published stroke QI interventions, with variable annual maintenance costs. Healthcare costs and outcomes (stroke, MI, major bleed, death) were modeled using 90-day and lifetime horizons. We calculated incremental cost-effectiveness ratios (ICER) and considered an ICER<$100,000 per quality-adjusted life year (QALY) to be cost-effective. Sensitivity analyses varying key inputs, including QI costs, were performed using Monte Carlo simulations.

Results: Compared to aspirin alone, DAPT use was not cost-effective at 90 days (ICER $173,003/QALY) but was cost saving ($3,030) and more effective (0.31 more QALYs) over a lifetime at current treatment rates. Increasing the use of DAPT by 20% with a QI intervention was not cost-effective at 90 days (ICER $474,467/QALY) but was cost-effective over a lifetime (ICER $29,217/QALY). Increasing DAPT use with a QI intervention was the preferred strategy in 89% of Monte Carlo runs (lifetime horizon). QI interventions to increase DAPT use were cost-effective over a range of annual costs (Figure).

Conclusion: In a modeling study, current rates of DAPT use after TIA/minor stroke are cost-effective over a lifetime, but a QI intervention to increase DAPT use is preferred in nearly all simulations.

Abstract TMP60: Misdiagnosis Of Posterior Reversible Encephalopathy Syndrome And Reversible Cerebral Vasoconstriction Syndrome In The Emergency Department

Introduction: Syndromes of cerebrovascular dysregulation such as posterior reversible encephalopathy syndrome (PRES) and reversible cerebral vasoconstriction syndrome (RCVS) can be challenging to diagnose given their rarity and the need for advanced neuroimaging to diagnose them. We sought to measure the rate of potential PRES/RCVS misdiagnosis in the ED and identify features associated with misdiagnosis.

Methods: We conducted a retrospective cohort study of patients with PRES/RCVS using deidentified administrative claims data from all nonfederal EDs and hospitals across 11 states from 2016-2018. To identify patients with PRES/RCVS, we used the previously validated ICD-10-CM codes I67.841 and I67.83. We defined patients with a probable misdiagnosis of PRES/RCVS as those with an ED visit resulting in discharge to home that occurred within the 14 days prior to their PRES/RCVS hospitalization. Only preceding ED visits where a non-specific neurological condition (e.g., headache, dizziness, numbness) was diagnosed were considered instances of probable ED misdiagnosis. Standard tests of comparison between patients with versus without probable misdiagnosis were used to identify patient-level and ED facility-level features associated with misdiagnosis.

Results: We identified 4,633 patients hospitalized for PRES/RCVS; the majority (4,169; 90.0%) had PRES. A total of 210 patients (4.5%, 95% CI: 3.95-5.17) had at least one preceding ED visit with a probable misdiagnosis; these patients were younger (mean age 47.7 vs. 53.8 years; P<0.001) and more often female (80.4% vs. 69.7%: P<0.001). Misdiagnosed patients generally had fewer vascular risk factors including hypertension (46.3% vs. 84.9%; P<0.001) and more often had a history of headache (81.1% vs. 22.6%; P<0.001) and psychiatric disease (48.6% vs. 34.9%; P<0.001) as compared to patients without an ED misdiagnosis. Facility factors inversely associated with probable misdiagnosis included an ACGME-approved residency (63.4% vs. 75.3%; P<0.001) and on-site neurological services (74.9% vs. 84.7%; P<0.001).

Conclusion: Probable ED misdiagnosis occurred in nearly 1 of 20 cases of PRES/RCVS in a large, multistate cohort.

Trends in Venous Thromboembolism Readmission Rates after Ischemic Stroke and Intracerebral Hemorrhage

BACKGROUND AND PURPOSE

Venous thromboembolism (VTE) is a life-threatening complication of stroke. We evaluated nationwide rates and risk factors for hospital readmissions with VTE after an intracerebral hemorrhage (ICH) or acute ischemic stroke (AIS) hospitalization.

METHODS

Using the Healthcare Cost and Utilization Project (HCUP) Nationwide Readmission Database, we included patients with a principal discharge diagnosis of ICH or AIS from 2016 to 2019. Patients who had VTE diagnosis or history of VTE during the index admission were excluded. We performed Cox regression models to determine factors associated with VTE readmission, compared rates between AIS and ICH and developed post-stroke VTE risk score. We estimated VTE readmission rates per day over a 90-day time window post-discharge using linear splines.

RESULTS

Of the total 1,459,865 patients with stroke, readmission with VTE as the principal diagnosis within 90 days occurred in 0.26% (3,407/1,330,584) AIS and 0.65% (843/129,281) ICH patients. The rate of VTE readmission decreased within first 4-6 weeks (P<0.001). In AIS, cancer, obesity, higher National Institutes of Health Stroke Scale (NIHSS) score, longer hospital stay, home or rehabilitation disposition, and absence of atrial fibrillation were associated with VTE readmission. In ICH, longer hospital stay and rehabilitation disposition were associated with VTE readmission. The VTE rate was higher in ICH compared to AIS (adjusted hazard ratio 2.86, 95% confidence interval 1.93-4.25, P<0.001).

CONCLUSIONS

After stroke, VTE readmission risk is highest within the first 4-6 weeks and nearly three-fold higher after ICH vs. AIS. VTE risk is linked to decreased mobility and hypercoagulability. Studies are needed to test short-term VTE prophylaxis beyond hospitalization in high-risk patients.

Factors Associated with Anticoagulation Initiation for New Atrial Fibrillation in an Urban Emergency Department

Objective

To explore factors associated with anticoagulation (AC) initiation after atrial fibrillation (AF) diagnosis.

Design

Retrospective cohort study.

Setting

Urban medical center.

Patients

Adults with emergency department (ED) diagnosis of new onset AF from 1/1/2017-1/1/2020 discharged home.

Methods

We compared patients initiated on AC, our primary outcome, to those not initiated on AC. Stroke, major bleeding, and AC initiation within 1 year of visit were secondary outcomes. We hypothesized that minority race and non-English language preference are associated with failure to initiate AC.

Results

Of 111 patients with AF, 88 met inclusion criteria. Mean age was 65 (SD 15); 47 (53%) were women. 49 (56%) patients were initiated on AC. Age (61 vs 68 years; P=.02), non-English language (28% vs 10%; P=.03), leaving ED against medical advice (AMA) (36% vs 14%; P=.04), and CHA²DS²-VASc score of 1 (41% vs 6%; P<=.001) were associated with no AC initiation. There were no associations between patient-reported race/ethnicity and AC. Cardiology consultation (83.67% vs 30.78%; P<.0001) and higher median CHA²DS²-VASc score (3[2-4]) vs. 2[1-4]; P=.047) were associated with AC. Of 73 patients with follow-up data at 1 year, 2 (8%) not initiated on AC had strokes, 2 (4%) initiated on AC had major bleeds, and 15 (62.5%) not initiated on AC in the ED subsequently were initiated on AC.

Conclusion

More than half of ED patients with new AF eligible for AC were initiated on it. Work to improve AC utilization among patients with new AF who left AMA from ED and those who prefer to communicate in a non-English language may be warranted.

Short-term stroke risk after emergency department treat-and-release headache visit

OBJECTIVE

To evaluate whether patients discharged to home after an emergency department (ED) visit for headache face a heightened short-term risk of stroke.

BACKGROUND

Stroke hospitalizations that occur soon after ED visits for headache complaints may reflect diagnostic error.

METHODS

We conducted a retrospective cohort study using statewide administrative claims data for all ED visits and admissions at nonfederal hospitals in Florida 2005-2018 and New York 2005-2016. Using standard International Classification of Diseases (ICD) codes, we identified adult patients discharged to home from the ED (treat-and-release visit) with a benign headache diagnosis (cohort of interest) as well as those with a diagnosis of renal colic or back pain (negative controls). The primary study outcome was hospitalization within 30 days for stroke (ischemic or hemorrhagic) defined using validated ICD codes. We assess the relationship between index ED visit discharge diagnosis and stroke hospitalization adjusting for patient demographics and vascular comorbidities.

RESULTS

We identified 1,502,831 patients with an ED treat-and-release headache visit; mean age was 41 (standard deviation: 17) years and 1,044,520 (70%) were female. A total of 2150 (0.14%) patients with headache were hospitalized for stroke within 30 days. In adjusted analysis, stroke risk was higher after headache compared to renal colic (hazard ratio [HR]: 2.69; 95% confidence interval [CI]: 2.29-3.16) or back pain (HR: 4.0; 95% CI: 3.74-4.3). In the subgroup of 26,714 (1.78%) patients with headache who received brain magnetic resonance imaging at index ED visit, stroke risk was only slightly elevated compared to renal colic (HR: 1.47; 95% CI: 1.22-1.78) or back pain (HR: 1.49; 95% CI: 1.24-1.80).

CONCLUSION

Approximately 1 in 700 patients discharged to home from the ED with a headache diagnosis had a stroke in the following month. Stroke risk was three to four times higher after an ED visit for headache compared to renal colic or back pain.

Laparoscopically Confirmed Endometriosis and Risk of Incident Stroke: A Prospective Cohort Study

BACKGROUND

Prior research suggests that women with endometriosis are at greater risk of coronary heart disease. Therefore, our objective was to prospectively investigate the association between laparoscopically confirmed endometriosis and risk of incident stroke during 28 years of follow-up.

METHODS

Participants in the NHSII cohort study (Nurses' Health Study II) were followed from 1989 when they were between the ages of 25 to 42 until 2017 for development of incident stroke (ischemic and hemorrhagic). Cox proportional hazard models were used to calculate hazard ratios and 95% CI, with adjustment for potential confounding variables (alcohol intake, body mass index at age 18, current body mass index, age at menarche, menstrual cycle pattern in adolescence, current menstrual cycle pattern, parity, oral contraceptive use history, smoking history, diet quality, physical activity, NSAID use, aspirin use, race/ethnicity, and income). We estimated the proportion of the total association mediated by history of hypertension, hypercholesterolemia, hysterectomy/oophorectomy, and hormone therapy. We also tested for effect modification by age (<50, ≥50 years), infertility history, body mass index (<25, ≥25 kg/m2), and menopausal status.

RESULTS

We documented 893 incident cases of stroke during 2 770 152 person-years of follow-up. Women with laparoscopically confirmed endometriosis had a 34% greater risk of stroke in multivariable-adjusted models (hazard ratio, 1.34 [95% CI, 1.10-1.62]), compared to those without a history of endometriosis. Of the total association of endometriosis with risk of stroke, the largest proportion was attributed to hysterectomy/oophorectomy (39% mediated [95% CI, 14%-71%]) and hormone therapy (16% mediated [95% CI, 5%-40%]). We observed no differences in the relationship between endometriosis and stroke by age, infertility history, body mass index, or menopausal status.

CONCLUSIONS

We observed that women with endometriosis were at elevated risk of stroke. Women and their health care providers should be aware of endometriosis history, maximize primary cardiovascular prevention, and discuss signs and symptoms of cardiovascular disease.

Cross-Sectional Retrospective Study to Identify Clinical and Radiographic Features Associated With VZV Reactivation in Cryptogenic Stroke Patients With CSF Testing

BACKGROUND AND PURPOSE

A large proportion of ischemic stroke patients lack a definitive stroke etiology despite extensive diagnostic testing. Varicella-Zoster Virus (VZV) can directly invade blood vessels causing vasculitis and may be associated with cryptogenic stroke (CS).

METHODS

We conducted a retrospective cross-sectional study of CS patients tested for VZV. The following were considered evidence of VZV reactivation (VZV+): positive CSF VZV PCR, anti-VZV IgM in CSF, or anti-VZV IgG CSF/serum ratio of 1:10 or higher. We describe the cohort, report VZV+ proportion with 95% confidence intervals (CI) determined with the Wald method, and compare patient groups using standard statistical tests.

RESULTS

A total of 72 CS patients met full study inclusion criteria. Most of the patients were <65 years old, had few traditional vascular risk factors, and had multifocal infarcts. Mean age was 49 years (SD ±13) and 47% were women. A total of 14 patients (19.4%; CI: 11.4-30.8%) had evidence of CNS VZV reactivation. There was no difference in evaluated demographic or radiographic features between those with versus without evidence of VZV reactivation. History of ischemic stroke in the past year (11/14 vs 25/43, P<.05) and hypertension (13/14 vs 35/58 and P<.05) were associated with VZV+.

CONCLUSION

We found a high proportion of CNS VZV reactivation in a cross-sectional cohort of CS patients selected for CSF testing. Testing for VZV might be reasonable in CS patients who are young, have multifocal infarcts, or had an ischemic stroke within the past year, but additional research is needed.

Direct Oral Anticoagulants Versus Warfarin in the Treatment of Cerebral Venous Thrombosis (ACTION-CVT): A Multicenter International Study

BACKGROUND

A small randomized controlled trial suggested that dabigatran may be as effective as warfarin in the treatment of cerebral venous thrombosis (CVT). We aimed to compare direct oral anticoagulants (DOACs) to warfarin in a real-world CVT cohort.

METHODS

This multicenter international retrospective study (United States, Europe, New Zealand) included consecutive patients with CVT treated with oral anticoagulation from January 2015 to December 2020. We abstracted demographics and CVT risk factors, hypercoagulable labs, baseline imaging data, and clinical and radiological outcomes from medical records. We used adjusted inverse probability of treatment weighted Cox-regression models to compare recurrent cerebral or systemic venous thrombosis, death, and major hemorrhage in patients treated with warfarin versus DOACs. We performed adjusted inverse probability of treatment weighted logistic regression to compare recanalization rates on follow-up imaging across the 2 treatments groups.

RESULTS

Among 1025 CVT patients across 27 centers, 845 patients met our inclusion criteria. Mean age was 44.8 years, 64.7% were women; 33.0% received DOAC only, 51.8% received warfarin only, and 15.1% received both treatments at different times. During a median follow-up of 345 (interquartile range, 140-720) days, there were 5.68 recurrent venous thrombosis, 3.77 major hemorrhages, and 1.84 deaths per 100 patient-years. Among 525 patients who met recanalization analysis inclusion criteria, 36.6% had complete, 48.2% had partial, and 15.2% had no recanalization. When compared with warfarin, DOAC treatment was associated with similar risk of recurrent venous thrombosis (aHR, 0.94 [95% CI, 0.51-1.73]; P=0.84), death (aHR, 0.78 [95% CI, 0.22-2.76]; P=0.70), and rate of partial/complete recanalization (aOR, 0.92 [95% CI, 0.48-1.73]; P=0.79), but a lower risk of major hemorrhage (aHR, 0.35 [95% CI, 0.15-0.82]; P=0.02).

CONCLUSIONS

In patients with CVT, treatment with DOACs was associated with similar clinical and radiographic outcomes and favorable safety profile when compared with warfarin treatment. Our findings need confirmation by large prospective or randomized studies.

Abstract TP72: Cost Effectiveness Of Smoking-Cessation Interventions Following Ischemic Stroke And Transient Ischemic Attack

Introduction: The cost effectiveness of smoking-cessation interventions after ischemic stroke and TIA has not been evaluated. We performed a cost-effectiveness analysis of smoking-cessation interventions in this population.

Methods: We constructed a decision tree model to compare brief counseling alone to 3 interventions: varenicline, any pharmacotherapy with intensive counseling, and monetary incentives. Direct health care costs of interventions and outcomes were modeled. The outcomes were recurrent stroke, myocardial infarction, and death using a 5-year horizon. Estimates and variance for the base case (42% cessation), costs and effectiveness of interventions, and outcome rates were imputed from the stroke literature. Using standard techniques, we calculated incremental cost-effectiveness ratios (ICER) and net-monetary benefits (NMB). An intervention was considered cost effective if the ICER was less than the standard willingness-to-pay threshold of $100,000 per quality-adjusted life year (QALY) or when the NMB was maximized. Sensitivity analyses and a probabilistic Monte Carlo simulation modeled the impact of parameter uncertainty, including for the base case cessation rate and costs and effectiveness of interventions (TreeAge Pro).

Results: All three interventions were cost effective based on the ICER: varenicline - $7,422/QALY, pharmacotherapy with counseling - $14,550/QALY, and monetary incentives - $23,280/QALY. In one-way sensitivity analyses, interventions costing up to $1,729 remained cost-effective. In a two-way sensitivity analysis varying the cost and effectiveness of smoking-cessation interventions, all three interventions were cost effective based on NMB (Figure). In 10,000 Monte Carlo simulations, smoking-cessation interventions were cost effective 90% of the time, as compared to brief counseling alone.

Conclusion: Smoking-cessation strategies are cost effective in secondary prevention after stroke and TIA.

Abstract WP115: Venous Thromboembolism Readmission In Acute Ischemic Stroke

Introduction: Venous thromboembolism (VTE) is a frequent and potentially life-threatening complication of acute ischemic stroke (AIS). We performed a nationwide analysis to evaluate rate and risk factors for VTE readmission in patients with AIS.

Methods: Using the Healthcare Cost and Utilization Project (HCUP) Nationwide Readmission Database, we included adult patients with a principal discharge diagnosis of AIS from 2016 to 2018. AIS, pulmonary embolism, deep vein thrombosis and other diagnosis were identified based on standard ICD-10 CM codes. Patients who had VTE diagnosis during the index admission were excluded. We determined 90-day VTE readmission rates and trends in patients with a principal diagnosis of AIS stratified by 30-day epochs. We then constructed a stepwise binary logistic regression model to determine odds ratios (OR) of demographic and clinical factors associated with VTE readmission rates.

Results: Of the 1,023,478 patients with AIS, 8378 (0.82%) had VTE during readmission and 2906 (0.28%) had VTE as principal diagnosis for readmission within 90 days of discharge. Among them, more than half (4557, 54.39% and 1581, 54.40%, respectively) of patients were readmitted within 30 days of discharge. The rate of VTE readmission decreased further away from index event (P < 0.001). In the Cox regression model, obesity (OR 1.48, 95% CI 1.24-1.76, P < 0.001), plegia of at least one limb (OR 1.24, 95% CI 1.08-1.43, P = 0.003), longer hospital length of stay (OR 1.02, 95% CI 1.01-1.02, P < 0.001), higher NIHSS (OR 1.04, 95% CI 1.03-1.05, P < 0.001) were associated with VTE readmission. Conversely, VTE readmission rates were lower in patients with a history of atrial fibrillation/flutter (OR 0.72, 95% CI 0.62-0.84, P < 0.001).

Conclusion: Patients with obesity, paralysis, higher NIHSS score, or prolonged hospital length of stay are at higher risk for VTE readmission. AF strokes are less likely to have DVT/PE, perhaps due to anticoagulant use in such patients. Studies are needed to determine whether early mobilization and mechanical and/or chemical prophylaxis reduces VTE risk in high-risk patients.

Abstract WMP55: Short-term Stroke Risk After Emergency Department Treat-and-release Headache Visit

Introduction: When a stroke hospitalization follows soon after an Emergency Department (ED) treat-and-release visit for non-specific neurological complaints, a diagnostic error may have occurred. In this study, we sought to evaluate potential stroke misdiagnoses after ED treat-and-release headache visits.

Methods: We conducted a retrospective cohort study using state-wide administrative claims data for all ED visits and admissions at nonfederal hospitals in Florida 2005-2018 and New York 2005-2016. Using standard ICD codes, we identified adult patients discharged home from the ED with a benign headache diagnosis (cohort of interest) as well as those with a diagnosis of back pain or renal colic (negative control cohorts). The primary study outcome was hospitalization within 30 days for stroke (ischemic or hemorrhagic), defined using validated ICD codes. We used Cox proportional hazards modeling to assess the relationship between the index ED visit reason and stroke hospitalization adjusting for demographics and vascular risk factors.

Results: We identified 1,458,904 patients with an ED treat-and-release headache visit; mean age was 41 (SD: 17) and 70% were female. A total of 2,636 (0.18%) headache patients were hospitalized for stroke within 30 days. Stroke risk was higher among headache patients compared to patients diagnosed with renal colic (HR: 2.7; 95% CI, 2.3-3.1) or back pain (HR: 3.8; 95% CI, 3.6-4.1; Figure). Among patients <40 years of age, stroke risk was even higher among headache as compared to back pain (HR: 10; 95% CI, 7.7-13.1); no strokes occurred in renal colic patients <40 years of age.

Conclusion: Approximately 1 in 500 patients discharged home from the ED with a headache diagnosis had a stroke in the following month. Stroke risk was 3-4 times higher after an ED visit for headache compared to back pain or renal colic. There may be opportunities to reduce diagnostic error among patients with ED visits for headache, particularly for those <40 years of age.

Abstract TMP101: Preoperative Atrial Fibrillation And Risk Of Stroke After Noncardiac Surgery

Objective: To assess rates of postoperative stroke after elective noncardiac surgery in patients with atrial fibrillation (AF).

Methods: We conducted a retrospective cohort study using all-payer administrative claims data on all non-federal hospitalizations and emergency department visits in 11 states between 2016 and 2018. We included patients hospitalized for elective noncardiac surgery, as defined by a surgical diagnosis related group and major diagnostic category codes. The exposure variable was preoperative AF. The outcome variable was ischemic stroke within 30 days of surgery. We performed survival analyses using Kaplan-Meier cumulative rates and Cox proportional hazards models. We stratified AF patients by their CHA 2 DS 2 -VASc score and tested its discrimination using the c-statistic.

Results: We identified 1,301,709 patients undergoing elective noncardiac surgery, of whom 94,363 (7.3%) had preoperative AF. Patients with AF were older (mean age, 73 versus 62 years) and had higher CHA 2 DS 2 -VASc scores (mean score, 3.2 vs 2.2). We identified 2,893 patients with postoperative stroke. The cumulative rate of postoperative stroke was 0.65% (95% CI, 0.60-0.70%) in patients with AF vs 0.19% (95% CI, 0.18-0.20%) in patients without AF. After adjustment for demographics and vascular risk factors, AF was associated with a higher risk of postoperative stroke (HR, 1.7; 95% CI, 1.5-1.8). Among AF patients, the CHA 2 DS 2 -VASc score was a good predictor of postoperative stroke (AUC, 0.81; 95% CI, 0.79-0.83). Rates of postoperative stroke among AF patients ranged from <0.1% in those with a CHA 2 DS 2 -VASc score of 0-2 to 14% in those with a score of 8 (Figure).

Conclusions: Patients with AF faced a heightened risk of postoperative stroke and this risk varied in proportion to the CHA 2 DS 2 -VASc score.

Abstract WP114: Elevated Troponin Is Associated With Mortality In Patients With Acute Cardioembolic Stroke And Atrial Fibrillation

Introduction: Stroke is the fifth leading cause of death in the US and a major cause of disability. Atrial fibrillation (AF) increases the risk of ischemic stroke fivefold. Cardioembolic stroke in patients with AF is associated with high mortality. The association of elevated cardiac troponin with mortality in patients with acute ischemic stroke has been studied previously; however, there is limited data in subgroups of ischemic stroke etiology. We sought to determine the association of troponin elevation at presentation with 90-day all-cause mortality in patients with acute ischemic stroke and AF.

Methods: The I nitiation of A nticoagulation after C ardioembolic Stroke (IAC) study is a multicenter cohort drawn from eight US Stroke Centers. We included consecutive patients hospitalized with acute ischemic stroke and AF between 2015-2018, who had an initial baseline cardiac troponin I (bcTnI) obtained at presentation. The primary outcome was all-cause mortality at 90 days from stroke onset. We undertook multivariable logistic regression to determine the association between elevated bcTnl (≥0.1 ng/mL) and 90-day mortality.

Results: Of the 2084 patients enrolled in IAC, 1889 patients had 90-day follow-up of which 1461 patients had bcTnI available. 239 of the included patients (16.4%) had an elevated bcTnl, and death within 90-days occurred in 323 patients (22.1%). Elevated bcTnI was associated with 90-day mortality in univariable analysis (49.4% vs 24.9%; OR 1.71, 95% CI 1.17-2.50, p<0.001). This association persisted after adjusting for potential confounders: age, NIHSS, coronary artery disease, congestive heart failure and initial systolic blood pressure (OR 1.71, 95% CI 1.17-2.50, p=0.006); and in sensitivity analysis adding CrCl to the adjusted model above (OR 1.57, 95% CI 1.03-2.39, p=0.037).

Conclusion: In acute ischemic stroke patients with AF, elevated bcTnI was independently associated with 90-day all-cause mortality.

Abstract WP57: Association Between Stroke Presentation During Off-hours And Mechanical Thrombectomy

Background: Access to mechanical thrombectomy in the US remains limited, in part due to a relative lack of trained interventionalists. Given potential staffing challenges, we hypothesized that access to thrombectomy would be worse on nights and weekends.

Methods: We used 2016-2018 all-payer claims data from all nonfederal emergency departments and acute care hospitals across 11 US states encompassing 80 million residents. Using recorded arrival times, hospital presentation was classified as on-hours if it fell between 8:00 a.m. and 6:00 p.m. on weekdays and as off-hours otherwise. For patients who underwent interhospital transfer, we used the arrival time at the initial hospital. We examined the association between off-hours arrival and mechanical thrombectomy using multiple logistic regression adjusted for age, sex, race/ethnicity, insurance type, socioeconomic status, urban-rural location of residence, the Charlson comorbidity index, initial presentation to a thrombectomy hub, and treatment with intravenous thrombolysis. We performed a sensitivity analysis limited to patients who presented with a probable large-vessel occlusion, defined as a documented NIHSS score ≥12, to a thrombectomy hub and underwent intravenous thrombolysis.

Results: Among 169,199 patients with ischemic strokes, the 82,784 (48.9%) who presented during off-hours had higher NIHSS scores (4 [IQR, 2-10] vs 2 [IQR, 1-9], P <0.001) and underwent thrombolysis more often (9.3% vs 8.5%, P <0.001). There were no differences between groups in rates of mechanical thrombectomy (3.4% on-hours vs 3.5% off-hours, P = 0.25). In adjusted models, off-hours presentation was not significantly associated with lower odds of mechanical thrombectomy (OR, 0.94; 95% CI, 0.85-1.03). Our findings were similar in a sensitivity analysis limited to patients with a probable large-vessel occlusion who initially presented to a thrombectomy hub and underwent intravenous thrombolysis (OR, 0.87; 0.69-1.09).

Conclusions: In a large population-based sample of ischemic stroke patients across the US, the odds of mechanical thrombectomy did not vary by time of presentation.

Infarct on Brain Imaging, Subsequent Ischemic Stroke, and Clopidogrel-Aspirin Efficacy: A Post Hoc Analysis of a Randomized Clinical Trial

IMPORTANCE

In the Platelet-Oriented Inhibition in New TIA and Minor Ischemic Stroke (POINT) trial, acute treatment with clopidogrel-aspirin was associated with significantly reduced risk of recurrent stroke. There may be specific patient groups who are more likely to benefit from this treatment.

OBJECTIVE

To investigate whether the association of clopidogrel-aspirin with stroke recurrence in patients with minor stroke or high-risk transient ischemic attack (TIA) is modified by the presence of infarct on imaging attributed to the index event (index imaging) among patients enrolled in the POINT Trial.

DESIGN, SETTING, AND PARTICIPANTS

In the POINT randomized clinical trial, patients with high-risk TIA and minor ischemic stroke were enrolled at 269 sites in 10 countries in North America, Europe, Australia, and New Zealand from May 28, 2010, to December 19, 2017. In this post hoc analysis, patients were divided into 2 groups according to whether they had an acute infarct on index imaging. All POINT trial participants with information available on the presence or absence of acute infarct on index imaging were eligible for this study. Univariable Cox regression models evaluated associations between the presence of an infarct on index imaging and subsequent ischemic stroke and evaluated whether the presence of infarct on index imaging modified the association of clopidogrel-aspirin with subsequent ischemic stroke risk. Data were analyzed from July 2020 to May 2021.

EXPOSURES

Presence or absence of acute infarct on index imaging.

MAIN OUTCOMES AND MEASURES

The primary outcome is whether the presence of infarct on index imaging modified the association of clopidogrel-aspirin with subsequent ischemic stroke risk.

RESULTS

Of the 4881 patients enrolled in POINT, 4876 (99.9%) met the inclusion criteria (mean [SD] age, 65 [13] years; 2685 men [55.0%]). A total of 1793 patients (36.8%) had an acute infarct on index imaging. Infarct on index imaging was associated with ischemic stroke during follow-up (hazard ratio [HR], 3.68; 95% CI, 2.73-4.95; P < .001). Clopidogrel-aspirin vs aspirin alone was associated with decreased ischemic stroke risk in patients with an infarct on index imaging (HR, 0.56; 95% CI, 0.41-0.77; P < .001) compared with those without an infarct on index imaging (HR, 1.11; 95% CI, 0.74-1.65; P = .62), with a significant interaction association (P for interaction = .008).

CONCLUSIONS AND RELEVANCE

In this study, the presence of an acute infarct on index imaging was associated with increased risk of recurrent stroke and a more pronounced benefit from clopidogrel-aspirin. Future work should focus on validating these findings before targeting specific patient populations for acute clopidogrel-aspirin treatment.

Cerebrovascular disease hospitalizations following emergency department headache visits: A nested case-control study

BACKGROUND

Delayed diagnosis of cerebrovascular disease (CVD) among patients can result in substantial harm. If diagnostic process failures can be identified at emergency department (ED) visits that precede CVD hospitalization, interventions to improve diagnostic accuracy can be developed.

METHODS

We conducted a nested case-control study using a cohort of adult ED patients discharged from a single medical center with a benign headache diagnosis from October 1, 2015 to March 31, 2018. Hospitalizations for CVD within 1 year of index ED visit were identified using a regional health information exchange. Patients with subsequent CVD hospitalization (cases) were individually matched to patients without subsequent hospitalization (controls) using patient age and visit date. Demographic, clinical, and ED process characteristics were assessed via detailed chart review. McNemar's test for categorical and paired t-test for continuous variables were used with statistical significance set at ≤0.05.

RESULTS

Of the 9157 patients with ED headache visits, 57 (0.6%, 95% confidence interval [CI] = 0.5-0.8) had a subsequent CVD hospitalization. Median time from ED visit to hospitalization was 107 days. In 25 patients (43.9%, 25/57) the CVD hospitalization and the index ED visit were at different hospitals. Fifty-three cases and 53 matched controls were included in the final study analysis. Cases and controls had similar baseline demographic and headache characteristics. Cases more often had a history of stroke (32.1% vs. 13.2%, p = 0.02) and neurosurgery (13.2% vs. 1.9%, p = 0.03) prior to the index ED visit. Cases more often had less than two components of the neurologic examination documented (30.2% vs. 11.3%, p = 0.03).

CONCLUSION

We found that 0.6% of patients with an ED headache visit had subsequent CVD hospitalization, often at another medical center. ED visits for headache complaints among patients with prior stroke or neurosurgical procedures may be important opportunities for CVD prevention. Documented neurologic examinations were poorer among cases, which may represent an opportunity for ED process improvement.

Treating High-Risk TIA and Minor Stroke Patients With Dual Antiplatelet Therapy: A National Survey of Emergency Medicine Physicians

BACKGROUND

Treatment with aspirin plus clopidogrel, dual antiplatelet therapy (DAPT), within 24 hours of high-risk transient ischemic attack (TIA) or minor stroke symptoms to eligible patients is recommended by national guidelines. Whether or not this treatment has been adopted by emergency medicine (EM) physicians is uncertain.

METHODS

We conducted an online survey of EM physicians in the United States. The survey consisted of 13 multiple choice questions regarding physician characteristics, practice settings, and usual approach to TIA and minor stroke treatment. We report participant characteristics and use chi-squared tests to compare between groups.

RESULTS

We included 162 participants in the final study analysis. 103 participants (64%) were in practice for >5 years and 96 (59%) were at nonacademic centers; all were EM board-certified or board-eligible. Only 9 (6%) participants reported that they would start DAPT for minor stroke and 8 (5%) reported that they would start DAPT after high-risk TIA. Aspirin alone was the selected treatment by 81 (50%) participants for minor stroke patients who presented within 24 hours of symptom onset and were not candidates for thrombolysis. For minor stroke, 69 (43%) participants indicated that they would defer medical management to consultants or another team. Similarly, 75 (46%) of participants chose aspirin alone to treat high-risk TIA; 74 (46%) reported they would defer medical management after TIA to consultants or another team.

CONCLUSION

In a survey of EM physicians, we found that the reported rate of DAPT treatment for eligible patients with high-risk TIA and minor stroke was low.

Emergency medicine physicians' perspectives on diagnostic accuracy in neurology: a qualitative study

OBJECTIVES

We sought to understand the knowledge, attitudes, and beliefs of emergency medicine (EM) physicians towards non-specific neurological conditions and the use of clinical decision support (CDS) to improve diagnostic accuracy.

METHODS

We conducted semi-structured interviews of EM physicians at four emergency departments (EDs) affiliated with a single US healthcare system. Interviews were conducted until thematic saturation was achieved. Conventional content analysis was used to identify themes related to EM physicians' perspectives on acute diagnostic neurology; directed content analysis was used to explore views regarding CDS. Each interview transcript was independently coded by two researchers using an iteratively refined codebook with consensus-based resolution of coding differences.

RESULTS

We identified two domains regarding diagnostic safety: (1) challenges unique to neurological complaints and (2) challenges in EM more broadly. Themes relevant to neurology included: (1) knowledge gaps and uncertainty, (2) skepticism about neurology, (3) comfort with basic as opposed to detailed neurological examination, and (4) comfort with non-neurological diseases. Themes relevant to diagnostic decision making in the ED included: (1) cognitive biases, (2) ED system/environmental issues, (3) patient barriers, (4) comfort with diagnostic uncertainty, and (5) concerns regarding diagnostic error identification and measurement. Most participating EM physicians were enthusiastic about the potential for well-designed CDS to improve diagnostic accuracy for non-specific neurological complaints.

CONCLUSIONS

Physicians identified diagnostic challenges unique to neurological diseases as well as issues related more generally to diagnostic accuracy in EM. These physician-reported issues should be accounted for when designing interventions to improve ED diagnostic accuracy.

Under Treatment of High-Risk TIA Patients with Clopidogrel-Aspirin in the Emergency Setting

BACKGROUND

Treating high-risk transient ischemic attack (TIA) with dual antiplatelet therapy (DAPT) reduces subsequent ischemic stroke risk yet current rates of clopidogrel-aspirin treatment are uncertain.

MATERIALS AND METHODS

We conducted a retrospective cohort study of consecutive TIA patients who presented to any of the four emergency departments (ED) of a single urban health system from 1/1/2018-3/1/2020. Medical record review was used to describe the cohort and assess clopidogrel-aspirin treatment. Patient eligibility for clopidogrel-aspirin was determined using relevant criteria from the Platelet-Oriented Inhibition in New TIA and Minor Ischemic Stroke (POINT) Trial. Comparisons among eligible patients who received versus did not receive clopidogrel-aspirin were conducted using t-test, chi-squared, and Mann-Whitney as indicated.

RESULTS

We identified 248 TIA patients of whom 95 met eligibility criteria for clopidogrel-aspirin treatment. Among these 95 patients, mean age was 69.5 (SD: 12), 68.4% were women, and median ABCD² score was 5 (IQR: 4-6). A total of 26/95 (27.4%) eligible patients received clopidogrel-aspirin within 24 hours of symptom onset. Appropriate clopidogrel-aspirin use was associated with having a stroke code called upon ED arrival (88.5% vs. 34.8%; P<0.001), being evaluated by a vascular neurologist (88.5% vs. 21.1%; P<0.001), and not presenting to the community ED site wherein only a single patient received clopidogrel-aspirin.

CONCLUSIONS

In a multisite, single health system study, nearly three-fourths of high-risk TIA patients eligible for clopidogrel-aspirin treatment did not receive it. Appropriate clopidogrel-aspirin use was highest among patients seen by vascular neurologists and lowest at the community ED, though under treatment was evident at all sites.

Ischaemic stroke on anticoagulation therapy and early recurrence in acute cardioembolic stroke: the IAC study

BACKGROUND AND PURPOSE

A subset of ischaemic stroke patients with atrial fibrillation (AF) have ischaemic stroke despite anticoagulation. We sought to determine the association between prestroke anticoagulant therapy and recurrent ischaemic events and symptomatic intracranial haemorrhage (sICH).

METHODS

We included consecutive patients with acute ischaemic stroke and AF from the Initiation of Anticoagulation after Cardioembolic stroke (IAC) study from eight comprehensive stroke centres in the USA. We compared recurrent ischaemic events and delayed sICH risk using adjusted Cox regression analyses between patients who were prescribed anticoagulation (ACp) versus patients who were naïve to anticoagulation therapy prior to the ischaemic stroke (anticoagulation naïve).

RESULTS

Among 2084 patients in IAC, 1518 had prior anticoagulation status recorded and were followed for 90 days. In adjusted Cox hazard models, ACp was associated with some evidence of a higher risk higher risk of 90-day recurrent ischaemic events only in the fully adjusted model (adjusted HR 1.50, 95% CI 0.99 to 2.28, p=0.058) but not increased risk of 90-day sICH (adjusted HR 1.08, 95% CI 0.46 to 2.51, p=0.862). In addition, switching anticoagulation class was not associated with reduced risk of recurrent ischaemic events (adjusted HR 0.41, 95% CI 0.12 to 1.33, p=0.136) nor sICH (adjusted HR 1.47, 95% CI 0.29 to 7.50, p=0.641).

CONCLUSION

AF patients with ischaemic stroke despite anticoagulation may have higher recurrent ischaemic event risk compared with anticoagulation-naïve patients. This suggests differing underlying pathomechanisms requiring different stroke prevention measures and identifying these mechanisms may improve secondary prevention strategies.

Statistical insights for crude-rate-based operational measures of misdiagnosis-related harms

In longitudinal event data, a crude rate is a simple quantification of the event rate, defined as the number of events during an evaluation window, divided by the at-risk population size at the beginning or mid-time point of that window. The crude rate recently received revitalizing interest from medical researchers who aimed to improve measurement of misdiagnosis-related harms using administrative or billing data by tracking unexpected adverse events following a "benign" diagnosis. The simplicity of these measures makes them attractive for implementation and routine operational monitoring at hospital or health system level. However, relevant statistical inference procedures have not been systematically summarized. Moreover, it is unclear to what extent the temporal changes of the at-risk population size would bias analyses and affect important conclusions concerning misdiagnosis-related harms. In this article, we present statistical inference tools for using crude-rate based harm measures, as well as formulas and simulation results that quantify the deviation of such measures from those based on the more sophisticated Nelson-Aalen estimator. Moreover, we present results for a generalized multibin version of the crude rate, for which the usual crude rate is a single-bin special case. The generalized multibin crude rate is more straightforward to compute than the Nelson-Aalen estimator and can reduce potential biases of the single-bin crude rate. For studies that seek to use multibin measures, we provide simulations to guide the choice regarding number of bins. We further bolster these results using a worked example of stroke after "benign" dizziness from a large data set.

Biomarkers of Coagulation and Inflammation in COVID-19-Associated Ischemic Stroke

[Figure: see text].

Effect of Alteplase Use on Outcomes in Patients With Atrial Fibrillation: Analysis of the Initiation of Anticoagulation After Cardioembolic Stroke Study

Background

Intravenous alteplase improves outcome after acute ischemic stroke without a benefit in 90‐day mortality. There are limited data on whether alteplase is associated with reduced mortality in patients with atrial fibrillation (AF)‐related ischemic stroke whose mortality rate is relatively high. We sought to determine the association of alteplase with hemorrhagic transformation and mortality in patients with AF.

Methods and Results

We retrospectively analyzed consecutive patients with acute ischemic stroke between 2015 and 2018 diagnosed with AF included in the IAC (Initiation of Anticoagulation After Cardioembolic Stroke) study, which pooled data from stroke registries at 8 comprehensive stroke centers across the United States. For our primary analysis, we included patients who did not undergo mechanical thrombectomy (MT), and secondary analyses included patients who underwent MT. We used binary logistic regression to determine whether alteplase use was associated with risk of hemorrhagic transformation and 90‐day mortality. There were 1889 patients (90.6%) who had 90‐day follow‐up data available for analyses and were included; 1367 patients (72.4%) did not receive MT, and 522 patients (27.6%) received MT. In our primary analyses we found that alteplase use was independently associated with an increased risk for hemorrhagic transformation (odds ratio [OR], 2.23; 95% CI, 1.57–3.17) but reduced risk of 90‐day mortality (OR, 0.58; 95% CI, 0.39–0.87). Among patients undergoing MT, alteplase use was not associated with a significant reduction in 90‐day mortality (OR, 0.68; 95% CI, 0.45–1.04).

Conclusions

Alteplase reduced 90‐day mortality of patients with acute ischemic stroke with AF not undergoing MT. Further study is required to assess the efficacy of alteplase in patients with AF undergoing MT.

Safer Stroke-Dx Instrument: Identifying Stroke Misdiagnosis in the Emergency Department

BACKGROUND

Missed or delayed diagnosis of acute stroke, or false-negative stroke (FNS), at initial emergency department (ED) presentation occurs in ≈9% of confirmed stroke patients. Failure to rapidly diagnose stroke can preclude time-sensitive treatments, resulting in higher risks of severe sequelae and disability. In this study, we developed and tested a modified version of a structured medical record review tool, the Safer Dx Instrument, to identify FNS in a subgroup of hospitalized patients with stroke to gain insight into sources of ED stroke misdiagnosis.

METHODS

We conducted a retrospective cohort study at 2 unaffiliated comprehensive stroke centers. In the development and confirmatory cohorts, we applied the Safer Stroke-Dx Instrument to report the prevalence and documented sources of ED diagnostic error in FNS cases among confirmed stroke patients upon whom an acute stroke was suspected by the inpatient team, as evidenced by stroke code activation or urgent neurological consultation, but not by the ED team. Inter-rater reliability and agreement were assessed using interclass coefficient and kappa values (κ).

RESULTS

Among 183 cases in the development cohort, the prevalence of FNS was 20.2% (95% CI, 15.0-26.7). Too narrow a differential diagnosis and limited neurological examination were common potential sources of error. The interclass coefficient for the Safer Stroke-Dx Instrument items ranged from 0.42 to 0.91, and items were highly correlated with each other. The κ for diagnostic error identification was 0.90 (95% CI, 0.821-0.978) using the Safer Stroke-Dx Instrument. In the confirmatory cohort of 99 cases, the prevalence of FNS was 21.2% (95% CI, 14.2-30.3) with similar sources of diagnostic error identified.

CONCLUSIONS

Hospitalized patients identified by stroke codes and requests for urgent neurological consultation represent an enriched population for the study of diagnostic error in the ED. The Safer Stroke-Dx Instrument is a reliable tool for identifying FNS and sources of diagnostic error.

Stroke hospitalization after misdiagnosis of "benign dizziness" is lower in specialty care than general practice: a population-based cohort analysis of missed stroke using SPADE methods

OBJECTIVES

Isolated dizziness is a challenging stroke presentation in the emergency department, but little is known about this problem in other clinical settings. We sought to compare stroke hospitalizations after treat-and-release clinic visits for purportedly "benign dizziness" between general and specialty care settings.

METHODS

This was a population-based retrospective cohort study from a national database. We included clinic patients with a first incident treat-and-release visit diagnosis of non-specific dizziness/vertigo or a peripheral vestibular disorder (ICD-9-CM 780.4 or 386.x [not 386.2]). We compared general care (internal medicine, family medicine) vs. specialty care (neurology, otolaryngology) providers. We used propensity scores to control for baseline stroke risk differences unrelated to dizziness diagnosis. We measured excess (observed>expected) stroke hospitalizations in the first 30 d (i.e., missed strokes associated with an adverse event).

RESULTS

We analyzed 144,355 patients discharged with "benign dizziness" (n=117,117 diagnosed in general care; n=27,238 in specialty care). After propensity score matching, patients in both groups were at higher risk of stroke in the first 30 d (rate difference per 10,000 treat-and-release visits for "benign dizziness" 24.9 [95% CI 18.6-31.2] in general care and 10.6 [95% CI 6.3-14.9] in specialty care). Short-term stroke risk was higher in general care than specialty care (relative risk, RR 2.2, 95% CI 1.5-3.2) while the long-term risk was not significantly different (RR 1.3, 95% CI 0.9-1.9), indicating higher misdiagnosis-related harms among dizzy patients who initially presented to generalists after adequate propensity matching.

CONCLUSIONS

Missed stroke-related harms in general care were roughly twice that in specialty care. Solutions are needed to address this care gap.

Cost-Effectiveness of Advanced Neuroimaging for Transient and Minor Neurological Events in the Emergency Department

Background Accurate diagnosis of patients with transient or minor neurological events can be challenging. Recent studies suggest that advanced neuroimaging can improve diagnostic accuracy in low-risk patients with transient or minor neurological symptoms, but a cost-effective emergency department diagnostic evaluation strategy remains uncertain. Methods and Results We constructed a decision-analytic model to evaluate 2 diagnostic evaluation strategies for patients with low-risk transient or minor neurological symptoms: (1) obtain advanced neuroimaging (magnetic resonance imaging brain and magnetic resonance angiography head and neck) on every patient or (2) current emergency department standard-of-care clinical evaluation with basic neuroimaging. Main probability variables were: proportion of patients with true ischemic events, strategy specificity and sensitivity, and recurrent stroke rate. Direct healthcare costs were included. We calculated incremental cost-effectiveness ratios, conducted sensitivity analyses, and evaluated various diagnostic test parameters primarily using a 1-year time horizon. Cost-effectiveness standards would be met if the incremental cost-effectiveness ratio was less than willingness to pay. We defined willingness to pay as $100 000 US dollars per quality-adjusted life year. Our primary and sensitivity analyses found that the advanced neuroimaging strategy was more cost-effective than emergency department standard of care. The incremental effectiveness of the advanced neuroimaging strategy was slightly less than the standard-of-care strategy, but the standard-of-care strategy was more costly. Potentially superior diagnostic approaches to the modeled advanced neuroimaging strategy would have to be >92% specific, >70% sensitive, and cost less than or equal to standard-of-care strategy's cost. Conclusions Obtaining advanced neuroimaging on emergency department patient with low-risk transient or minor neurological symptoms was the more cost-effective strategy in our model.

Head Computed tomography during emergency department treat-and-release visit for headache is associated with increased risk of subsequent cerebrovascular disease hospitalization

OBJECTIVES

The occurrence of head computed tomography (HCT) at emergency department (ED) visit for non-specific neurological symptoms has been associated with increased subsequent stroke risk and may be a marker of diagnostic error. We evaluate whether HCT occurrence among ED headache patients is associated with increased subsequent cerebrovascular disease risk.

METHODS

We conducted a retrospective cohort study of consecutive adult patients with headache who were discharged home from the ED (ED treat-and-release visit) at one multicenter institution. Patients with headache were defined as those with primary ICD-9/10-CM discharge diagnoses codes for benign headache from 9/1/2013-9/1/2018. The primary outcome of cerebrovascular disease hospitalization was identified using ICD-9/10-CM codes and confirmed via chart review. We matched headache patients who had a HCT (exposed) to those who did not have a HCT (unexposed) in the ED in a one-to-one fashion using propensity score methods.

RESULTS

Among the 28,121 adult patients with ED treat-and-release headache visit, 45.6% (n=12,811) underwent HCT. A total of 0.4% (n=111) had a cerebrovascular hospitalization within 365 days of index visit. Using propensity score matching, 80.4% (n=10,296) of exposed patients were matched to unexposed. Exposed patients had increased risk of cerebrovascular hospitalization at 365 days (RR: 1.65: 95% CI: 1.18-2.31) and 180 days (RR: 1.62; 95% CI: 1.06-2.49); risk of cerebrovascular hospitalization was not increased at 90 or 30 days.

CONCLUSIONS

Having a HCT performed at ED treat-and-release headache visit is associated with increased risk of subsequent cerebrovascular disease. Future work to improve cerebrovascular disease prevention strategies in this subset of headache patients is warranted.

Abstract P12: Alteplase Reduces Mortality in Patients With Ischemic Stroke and Atrial Fibrillation: Analysis of the IAC Study

Background and Purpose: Multiple studies have established that intravenous thrombolysis with alteplase improves outcome after acute ischemic stroke. However, assessment of thrombolysis’ efficacy in stroke patients with atrial fibrillation (AF) has yielded mixed results. We sought to determine the association of alteplase with mortality, hemorrhagic transformation (HT), infarct volume, and mortality in patients with AF and acute ischemic stroke.

Methods: We retrospectively analyzed consecutive acute ischemic stroke patients with AF included in the Initiation of Anticoagulation after Cardioembolic stroke (IAC) study, which pooled data from 8 comprehensive stroke centers in the United States. 1889 (90.6%) had available 90-day follow up data and were included. For our primary analysis we used a cohort of 1367/1889 (72.4%) patients who did not undergo mechanical thrombectomy (MT). Secondary analyses were repeated in the patients that underwent MT (n=522). Binary logistic regression was used to determine whether alteplase use was independently associated with risk of HT, final infarct volume, and 90-day mortality, respectively, adjusting for potential confounders.

Results: In our primary analyses we found that alteplase use was independently associated with an increased risk for HT (adjusted OR 2.14, 95% CI 1.49 - 3.07, p <0.001) but overall reduced risk of 90-day mortality (adjusted OR 0.58, 95% CI 0.39 - 0.87, p = 0.009). Among patients undergoing MT, alteplase use was associated with a trend towards a reduction in 90-day mortality (adjusted OR 0.68 95% CI 0.45 - 1.04, p = 0.077). In the subgroup of patients prescribed DOAC treatment (n = 327; 24 received alteplase), alteplase treatment was associated with a trend towards smaller infarct size (< 10 mL), (adjusted OR 0.40, 95% CI 0.15 - 1.12, p = 0.082) without a significant difference in the odds of 90-day mortality (adjusted OR 0.51, 95% CI 0.12 - 2.13, p = 0.357) or hemorrhagic transformation (adjusted OR 0.27, 95% CI 0.03 - 2.07, p = 0.206).

Conclusion: Thrombolysis with intravenous alteplase was associated with reduced 90-day mortality in AF patients with acute ischemic stroke not undergoing MT. Further study is required to assess the safety and efficacy of alteplase in AF patients undergoing MT and those on DOACs.

Abstract P90: Clinical Features of Patients With Cryptogenic Stroke and Covid-19

Introduction: While coronavirus disease 2019 (COVID-19) has been associated with acute ischemic stroke (AIS), the causal relationship has yet to be elucidated. Factors that likely confer increased stroke risk are COVID-19-associated coagulopathy and hyperinflammatory response. Studying clinical features of patients with otherwise undetermined cause of AIS could help better define COVID-19-associated stroke.

Methods: We performed a multicenter cross-sectional study of consecutive patients presenting with AIS and COVID-19 to one of two large healthcare systems in New York City during the local COVID-19 surge from March 1, 2020 to May 31, 2020. In-hospital stroke cases were excluded. We compared demographic and clinical features of patients with COVID-19 and a cryptogenic AIS subtype to patients with COVID-19 and a determined subtype. Baseline characteristics and clinical variables were compared using chi-squared and Fisher exact tests.

Results: A total of 62 patients with AIS and COVID-19 at the time of hospital arrival were identified. Of these, 30 were classified as having a cryptogenic subtype (80% after complete diagnotics evaluation), and 32 had an identifiable stroke mechanism. Patients with cryptogenic AIS were significantly younger (p=0.011) and less likely to have co-morbid hypertension (p=0.019), coronary artery disease (p=0.024), heart failure (p=0.039), atrial fibrillation (<0.0001), and prior stroke or TIA (p=0.033) compared to those with defined mechanisms. Further, d-dimer, but not C-reactive protein, was significantly higher in patients with cryptogenic stroke compared to those with defined causes (p=0.009).

Conclusion: Patients with AIS in the setting of COVID-19 and no other determined stroke mechanism were younger, less likely to have classic risk factors, and had higher d-dimer levels when compared to those with a determined mechanism. Further study of COVID-19-associated hypercoagulability as a mechanism of stroke is warranted.

Abstract P26: Association of Tranexamic Acid Use With Outcomes in Alteplase-Associated Intracranial Hemorrhage

Background: Alteplase (tPA) is the standard of care in acute ischemic stroke (AIS) treatment, but it is associated with increased risk of symptomatic intracranial hemorrhage (sICH). Cryoprecipitate (Cryo) is recommended for tPA-associated sICH reversal. Tranexamic acid (TXA), an antifibrinolytic, is of interest as an adjunct therapy, but data in AIS is limited. We aim to assess the relationship of TXA and sICH reversal.

Methods: We conducted a multicenter retrospective cohort study of AIS patients admitted between April 2015 and July 2020 who were treated for tPA-associated sICH. Patients with extracranial bleeds, who were not reversed, or who died within 24 hours were excluded. Demographics, clinical characteristics, imaging, and outcome data were collected from electronic health records. Outcomes included hematoma expansion, a poor functional outcome at 90 days (modified Rankin Score 3-6), and thrombotic events. We used Pearson chi-square, Fisher’s exact, and Wilcoxon rank-sum tests to compare outcomes between adjunct TXA treatment (TXA+Cryo) vs. Cryo only groups.

Results: The study cohort included 30 patients with tPA-related sICH (mean age 80 ±12.4 years; 60% female). Overall median (IQR) hematoma size was 4.4 ml (1.1-20). Multifocal bleeds were present in 39% of patients. TXA+Cryo was administered in 16 (53%) patients. Initial hematoma size was smaller in the TXA+Cryo group than the Cryo only group, median (IQR) of 2.4 ml (0.5-14.3) vs 24.1 ml (2.5-56.5), p=0.043. However, there were no marked differences between TXA+Cryo and the Cryo only groups for hematoma expansion (5 [33%] vs. 6 [50%] patients, p=0.38), poor functional outcome (15 [94%] vs. 11 [79%] patients, p=0.32), or thrombotic events (1 [6%] vs. 0, p=1.00).

Conclusion: Among patients treated for tPA-related sICH, there was no difference in hematoma expansion, poor functional outcome, or thrombotic events in patients treated with adjunct TXA compared to Cryo alone.