An Age-Adjusted D-dimer Threshold for Emergency Department Patients With Suspected Pulmonary Embolus: Accuracy and Clinical Implications

Evaluating outcomes of patients with suspected pulmonary embolism using an age-adjusted cutoff with a D-dimer unit-based assay

INTRODUCTION

Studies have suggested that an age-adjusted D-dimer (AADD) could improve specificity while maintaining sensitivity for the diagnosis of pulmonary embolism (PE). Most laboratories and published data report D-dimer in fibrinogen equivalent units, but some laboratory assays report using D-dimer units (DDU). However, only two small studies have examined AADD with a DDU-based assay. Our study aims to assess the sensitivity and specificity of AADD cutoffs, compared to the conventional cutoffs, in a large cohort of patients who underwent D-dimer testing using a DDU-based assay, for suspected PE.

METHODS

We included 1831 patients who presented to the emergency department and underwent a diagnostic workup that included a D-dimer test followed by computed tomography pulmonary angiography (CTA). The laboratory utilized the HemosIL D-Dimer HS reagent, reporting D-dimer values in DDU (ng/mL). We retrospectively adjusted D-dimer levels for patients using the formula: age (years) x 5 ng/mL. This adjustment created a comparison group to evaluate the test characteristics of the AADD cutoff compared to the conventional cutoff.

RESULTS

The conventional D-dimer cutoff of 230 ng/mL had a sensitivity of 97.4 % (95 % Confidence Interval [CI]: 95.3-99.4 %), specificity of 7.3 % (CI: 6.0-8.6 %), positive predictive value (PPV) of 13 % (CI: 11.4-14.6 %), and negative predictive value (NPV) of 95.1 % (CI: 91.3-98.9 %). The AADD cutoff had a sensitivity of 96.1 % (CI: 93.5-98.6 %), specificity of 16.6 % (CI: 14.8-18.4 %), PPV of 14.1 % (CI: 12.3-15.8 %), and NPV of 96.7 % (CI: 94.6-98.8 %).

CONCLUSION

In this study using a DDU-based assay, the specificity of the AADD cutoff was greater while the sensitivity was similar to that of the unadjusted cutoff, with no statistically significant difference observed.

Overuse of Computed Tomography Pulmonary Angiography in the Diagnosis of Pulmonary Thromboembolism "Real-Life Data"

Purpose

Pulmonary thromboembolism (PTE) is a common cause of cardiovascular mortality with an increasing incidence rate. Scoring patients with suspected pulmonary thromboembolism according to their symptoms, findings, and risk factors is useful for empirical diagnosis and management. The combination of D-dimer and clinical scoring allows the diagnosis to be excluded in approximately 30% of patients with suspected PTE without the need for imaging methods. Despite this, clinical scores are not used effectively in the clinic. The aim of this study is to show that computed tomography pulmonary angiography (CTPA) is overused in real life and to emphasize that overuse of CTPA can be prevented with clinical tests.

Patients and Methods

We studied 214 patients who underwent CTPA for suspected pulmonary thromboembolism. We evaluated whether clinical probability scoring (Wells scoring, Geneva scoring) was performed prior to CTPA from these patients' records and the health system database, and if so, the scores were evaluated. The rates and results of PERC criteria were also evaluated in patients.

Results

Pulmonary thromboembolism was not detected on CTPA in 185 patients (86.4%). PERC criteria were not evaluated in all patients before CTPA. When the PERC criteria were evaluated by the study team, it was found that there was a significant relationship between PTE diagnosis and the criteria. There was also a significant correlation between Geneva score and CTPA results (p=0.000<0.05).

Conclusion

Preventing overuse of CTPA by evaluating clinical probability scores, PERC criteria and d-dimer levels is important in many ways. Prevention of overuse of CTPA use will reduce unnecessary workload in clinical functioning and provide financial gain. Although CTPA is a diagnostic method with high diagnostic accuracy in the diagnosis of PTE, it is overused in real life. The overuse of CTPA can be significantly reduced by the combined use of clinical probability scoring (Wells and Geneva), exclusion criteria (PERC) and d-dimer results.

Sex differences in guideline-consistent diagnostic testing for acute pulmonary embolism among adult emergency department patients aged 18-49

BACKGROUND

Pulmonary embolism (PE) is a frequent diagnostic consideration in emergency department (ED) patients, yet diagnosis is challenging because symptoms of PE are nonspecific. Guidelines recommend the use of clinical decision tools to increase efficiency and avoid harms from overtesting, including D-dimer screening in patients not at high risk for PE. Women undergo testing for PE more often than men yet have a lower yield from testing. Our study objective was to determine whether patient sex influenced the odds of received guideline-consistent care.

METHODS

We performed a retrospective cohort study at two large U.S. academic EDs from January 1, 2016, to December 31, 2018. Nonpregnant patients aged 18-49 years were included if they presented with chest pain, shortness of breath, hemoptysis, or syncope and underwent testing for PE with D-dimer or imaging. Demographic and clinical data were exported from the electronic medical record (EMR). Pretest risk scores were calculated using manually abstracted EMR data. Diagnostic testing was then compared with recommended testing based on pretest risk. The primary outcome was receipt of guideline-consistent care, which required an elevated screening D-dimer prior to imaging in all non-high-risk patients.

RESULTS

We studied 1991 discrete patient encounters; 37% (735) of patients were male and 63% (1256) were female. Baseline characteristics, including revised Geneva scores, were similar between sexes. Female patients were more likely to receive guideline-consistent care (70% [874/1256] female vs. 63% [463/735] male, p < 0.01) and less likely to be diagnosed with PE (3.1% [39/1256] female vs. 5.3% [39/735] male, p < 0.05). The most common guideline deviation in both sexes was obtaining imaging without a screening D-dimer in a non-high-risk patient (75% [287/382] female vs. 75% [205/272] male).

CONCLUSIONS

In this cohort, females were more likely than males to receive care consistent with current guidelines and less likely to be diagnosed with PE.

A study of modified Wells score for pulmonary embolism and age-adjusted D-dimer values in patients at risk for deep venous thrombosis

Aims

Pulmonary embolism (PE) is the most severe complication of deep venous thrombosis (DVT). This study was designed to evaluate the usefulness of modified Wells score combined with age-adjusted D-dimer cut-off levels as a clinical pre-test probability assessment for predicting PE in patients 'at risk for DVT.'

Methods

This was a cross-sectional study including 200 in-patients at risk for DVT. Patients were categorized as 'pulmonary embolism unlikely' or 'pulmonary embolism likely' using modified Wells score and underwent D-dimer testing. PE was considered excluded in patients classified as unlikely with normal D-dimer levels, whereas the rest of the patients underwent computed tomography pulmonary angiogram (CTPA).

Results

Out of 200 patients, 163 patients (81.50%) were 'pulmonary embolism unlikely,' whereas 37 patients (18.50%) were 'pulmonary embolism likely.' Of 163 patients categorized as 'pulmonary embolism unlikely,' 67 patients (41.5%) had normal D-dimer values and were excluded from CTPA. PE was detected in 24.2% of the patients who underwent CTPA.

Conclusion

The combined strategy using modified Wells score and age-adjusted D-dimer cut-off value has 100% sensitivity and a negative predictive value and can be used to safely exclude PE in in-patients.

Application of the pulmonary embolism rule-out criteria (PERC rule) and age-adjusted D-Dimer in patients undergoing computed tomography pulmonary angiography for diagnosis of pulmonary embolism

Background

Diagnosis of pulmonary embolism (PE) constitutes a challenge for practitioners. Current practice involves use of pre-test probability prediction rules. Several strategies to optimize this process have been explored.

Objectives

To explore whether application of the pulmonary embolism rule-out criteria (PERC rule) and age-adjusted D-dimer (DD) would have reduced the number of computed tomography pulmonary angiography (CTPA) examinations performed in patients with suspected PE.

Methods

A retrospective cross-sectional study of adult patients taken for CTPA under suspicion of PE in 2018 and 2020. The PERC rule and age-adjusted DD were applied. The number of cases without indications for imaging studies was estimated and the operational characteristics for diagnosis of PE were calculated.

Results

302 patients were included. PE was diagnosed in 29.8%. Only 27.2% of 'not probable' cases according to the Wells criteria had D-dimer assays. Age adjustment would have reduced tomography use by 11.1%, with an AUC of 0.5. The PERC rule would have reduced use by 7%, with an AUC of 0.72.

Conclusions

Application of age-adjusted D-dimer and the PERC rule to patients taken for CTPA because of suspected PE seems to reduce the number of indications for the procedure.

Diagnostic performance of D-dimer in predicting venous thromboembolism and acute aortic dissection

BACKGROUND

D-dimer is elevated in a variety of conditions. The purpose of this study was to assess the positive predictive value of D-dimer to rule in patients with confirmed pulmonary embolism, deep vein thrombosis, acute aortic dissection or thrombosis of the upper extremity in comparison to patients with elevated D-dimer for other reasons.

METHODS AND RESULTS

We studied 1334 patients presenting to the emergency department with pulmonary embolism (n=193), deep vein thrombosis (n=73), acute aortic dissection (n=22), thrombosis of the upper extremity (n=8) and 1038 controls. The positive predictive value was increased with higher D-dimer concentrations improving the ability to identify diseases with high thrombus burden. Patients with venous thromboembolism, acute aortic dissection and thrombosis of the upper extremity showed a maximum positive predictive value of 85.2% at a D-dimer level of 7.8 mg/L (95% confidence interval (CI) 78.1 to 90.4). The maximum positive predictive value was lower in cancer patients with venous thromboembolism, acute aortic dissection and thrombosis of the upper extremity, reaching 68.9% at a D-dimer level of 7.5 mg/L (95% CI 57.4 to 78.4). The positive likelihood ratio was very consistent with the positive predictive value. Using a cut-off level of 0.5 mg/L, D-dimer showed a high sensitivity of at least 93%, but a very low specificity of nearly 0%. Conversely, an optimised cut-off value of 4.6 mg/L increased specificity to 95% for the detection of life-threatening venous thromboembolism, acute aortic dissection or thrombosis of the upper extremity at the costs of moderate sensitivities (58% for pulmonary embolism, 41% for deep vein thrombosis, 65% for pulmonary embolism with co-existent deep vein thrombosis, 50% for acute aortic dissection and 13% for thrombosis of the upper extremity). Using the same cut-off in cancer patients, higher values were observed for sensitivity at a specificity level of more than 95%. The area under the curve for the discrimination of venous thromboembolism/acute aortic dissection/thrombosis of the upper extremity from controls was significantly higher in cancer versus non-cancer patients (area under the curve 0.905 in cancer patients, 95% CI 0.89 to 0.92, vs. area under the curve 0.857 in non-cancer patients, 95% CI 0.84 to 0.88; P=0.0349).

CONCLUSION

D-dimers are useful not only to rule out but also to rule in venous thromboembolism and acute aortic dissection with an at least moderate discriminatory ability, both in patients with and without cancer.

Crucial considerations: Sex differences in the epidemiology, diagnosis, treatment, and outcomes of acute pulmonary embolism in non-pregnant adult patients

Acute pulmonary embolism (PE) affects over 600,000 Americans per year and is a common diagnostic consideration among emergency department patients. Although there are well-documented differences in the diagnosis, treatment, and outcomes of cardiovascular conditions, such as ischemic heart disease and stroke, the influence of sex and gender on PE remains poorly understood. The overall age-adjusted incidence of PE is similar in women and men, but women have higher relative rates of PE during early and mid-adulthood (ages 20-40 years); whereas, men have higher rates of PE after age 60 years. Women are tested for PE at far higher rates than men, yet women who undergo computed tomography pulmonary angiography are ultimately diagnosed with PE 35%-55% less often than men. Among those diagnosed with PE, women are more likely to have severe clinical features, such as hypotension and signs of right ventricular dysfunction. When controlled for PE severity, women are less likely to receive reperfusion therapies, such as thrombolysis. Finally, women have more bleeding complications for all types of anticoagulation. Further investigation of possible sex-specific diagnostic and treatment algorithms is necessary in order to more accurately detect and treat acute PE in non-pregnant adults.

Effect of Using an Age-adjusted D-dimer to Assess for Pulmonary Embolism in Community Emergency Departments

BACKGROUND

The objective of this study was to evaluate the effect of changing the laboratory-reported D-dimer reference intervals to age-adjusted reference intervals on the use of advanced chest imaging and 30-day adverse events among emergency department (ED) encounters.

METHODS

A retrospective interrupted time-series analysis of ED encounters for patients > 50 years evaluated for suspected pulmonary embolism (PE) from April 2014 to April 2016. The primary outcome was use of advanced diagnostic imaging, and the secondary outcome was 30-day mortality or PE diagnosis. Secondary analyses also quantified delayed PE diagnoses pre- and postintervention. A generalized estimating equation segmented logistic regression model, adjusting for patient and facility characteristics, was used to determine changes in odds of diagnostic imaging and 30-day mortality or PE diagnoses.

RESULTS

A total of 10,534 (5,153 pre- and 5,381 postimplementation) ED encounters were included. Advanced imaging was obtained in 35.9% of pre- versus 33% of postimplementation encounters. Age-adjusted D-dimer (AADD) showed a small and nonsignificant decrease in month-to-month trends of advanced chest imaging postimplementation (odds ratio [OR] = 0.98, 95% confidence interval [CI] = 0.96 to 1.00). Use of advanced imaging in patients with D-dimer values lower than 500 ng/mL fibrinogen-equivalent units (FEU) was similar in the preintervention (5.8%) and postintervention (6.8%) periods. However, imaging was obtained in 30% of patients postintervention with a D-dimer result less than AADD reference interval , but more than the historical 500 ng/mL FEU reference interval. Implementing an AADD threshold demonstrated no change in the rate of 30-day adverse events (missed PE or mortality).

CONCLUSION

Changing the laboratory-reported D-dimer reference intervals for evaluation of PE was not associated with reduction in advanced chest imaging and did not increase 30-day adverse events. However, there was substantial noncompliance with the age-adjusted reference intervals in the postintervention period likely blunting the impact of this intervention.

Multi-center implementation of automated age-adjusted D-dimer results reduces unnecessary PE imaging

BACKGROUND

Several previous studies have investigated the clinical utility of age-adjusted D-dimer cutoffs for diagnosing pulmonary embolism (PE).

OBJECTIVES

We performed a pre/post implementation study, using data from a mid-Atlantic healthcare system comprising 6 hospitals and 400,000 ED visits to determine whether implementing age adjusted D-dimer cutoffs reduced the number of imaging tests performed.

METHODS

Retrospective study of all patients who had a D-dimer performed during ED visits between September 2015 to September 2018. On March 21, 2017, the D-dimer upper limit of normal system-wide was increased for patients over 50 to: Age (years) x 0.01μg/mL. D-dimer results were displayed as normal or high based on automated age adjustment. EHR Chart review was performed 1.5 years prior to implementation of age-adjusted D-dimer cutoffs, as well as 1.5 years after to evaluate mortality and test accuracy characteristics such as false negative rates. Comparisons were made using chi-square testing.

RESULTS

22,302 D-dimers were performed pre-implementation of which 10,837 (48.6%) were positive resulting in 7218 (32.3%) imaging studies. After implementation of age-adjusted d-dimer, 25,082 were performed of which 10,851 (43.2%) were positive resulting in 7017 (28.0%) imaging studies. (pre: 48.6%, post: 43.2%; p < 0.01). A significantly lower proportion of patients had a positive d-dimer (pre: 48.6%, post: 43.2%; p < 0.01) and underwent imaging post-implementation (pre: 32.3%, post: 28.0%; p < 0.05) a relative risk reduction of 13.3. This absolute risk reduction of 4.4% is associated with 1104 less scans in the post-implementation group while still increasing test accuracy from 53.7% to 59.2% (p < 0.05).

CONCLUSION

Implementation of an automated age-adjusted D-dimer positive reference value reduced CT and V/Q imaging in this population by 4.4% while increasing test accuracy in a regional, heterogeneous six-hospital system.

Acute pulmonary embolism multimodality imaging prior to endovascular therapy

The manuscript discusses the application of CT pulmonary angiography, ventilation–perfusion scan, and magnetic resonance angiography to detect acute pulmonary embolism and to plan endovascular therapy. CT pulmonary angiography offers high accuracy, speed of acquisition, and widespread availability when applied to acute pulmonary embolism detection. This imaging modality also aids the planning of endovascular therapy by visualizing the number and distribution of emboli, determining ideal intra-procedural catheter position for treatment, and signs of right heart strain. Ventilation–perfusion scan and magnetic resonance angiography with and without contrast enhancement can also aid in the detection and pre-procedural planning of endovascular therapy in patients who are not candidates for CT pulmonary angiography.

Ideal high sensitivity troponin baseline cutoff for patients with renal dysfunction

OBJECTIVE

High-sensitivity cardiac troponin assays (hs-cTn) aid in diagnosis of myocardial infarction (MI). These assays have lower specificity for non-ST Elevation MI (NSTEMI) in patients with renal disease. Our objective was to determine an optimized cutoff for patients with renal disease.

METHODS

We conducted an a priori secondary analysis of a prospective FDA study in adults with suspected MI presenting to 29 academic urban EDs between 4/2015 and 4/2016. Blood was drawn 0, 1, 2-3, and 6-9 h after ED arrival. We recorded cTn and estimated glomerular filtrate rate (eGFR) by Chronic Kidney Disease Epidemiology Collaboration equation. The primary endpoint was NSTEMI (Third Universal Definition of MI), adjudicated by physicians blinded to hs-cTn results. We generated an adjusted hscTn rule-in cutoff to increase specificity.

RESULTS

2505 subjects were enrolled; 234 were excluded. Patients were mostly male (55.7%) and white (57.2%), median age was 56 years 472 patients [20.8%] had an eGFR <60 mL/min/1.73 m2. In patients with eGFR <15 mL/min/1.73 m2, a baseline rule-in cutoff of 120 ng/L led to a specificity of 85.0% and Positive Predictive Value (PPV) of 62.5% with 774 patients requiring further observation. Increasing the cutoff to 600 ng/L increased specificity and PPV overall and in every eGFR subgroup (specificity and PPV 93.3% and 78.9%, respectively for eGFR <15 mL/min/1.73m²), while increasing the number (79) of patients requiring observation.

CONCLUSIONS

An eGFR-adjusted baseline rule-in threshold for the Siemens Atellica hs-cTnI improves specificity with identical sensitivity. Further study in a prospective cohort with higher rates of renal disease is warranted.

Diagnostic utility of an age-specific cut-off for d-dimer for pulmonary embolism assessment when used with various pulmonary embolism risk scores

This retrospective cohort study compared the diagnostic utility (sensitivity, specificity and negative predictive value (NPV)) of the age-times-10 adjusted d-dimer cut-off used in combination with the original and simplified Well's pulmonary embolism (PE) scores and the original and simplified revised Geneva scores to identify patients in whom PE is classified as unlikely according to each score. The PE risk scores performed similarly with high sensitivity (97.6, 97.1, 96.9 and 97.1% respectively) and NPV (99.3, 99.3, 99.2 and 99.2% respectively). Each missed only one PE. The age-times-10 age-adjusted d-dimer assay cut-off performed similarly with each of the clinical risk scores tested with high sensitivity and NPV.

Appropriate Use of Venous Imaging and Analysis of the D-Dimer/Clinical Probability Testing Paradigm in the Diagnosis and Location of Deep Venous Thrombosis

BACKGROUND

The D-dimer (DD) level combined with the pretest Wells criteria probability (WCP) score can safely exclude deep venous thrombosis (DVT). The objective of this study was to examine the correlation between DD results alongside WCP score with findings on venous duplex ultrasound (VDU). The hypothesis is that VDU remains overutilized in low-risk patients with negative DD and that higher DD levels may correlate with thrombus burden and location.

METHODS

Patients who presented to a high-volume tertiary care center with lower limb swelling with or without associated pain were retrospectively examined through June and July for 4 consecutive years (2012 to 2015). After calculating WCP, patients were divided into low-, moderate-, and high-risk categories. Electronic DD results utilizing enzyme linked immunosorbent assay, WCP data, and VDU analysis data were merged and analyzed based on receiver operator characteristic curve to determine the DD cutoff point for each WCP. Abnormal DD with an average value ≥ 0.6 mg/L fibrinogen equivalent units (FEUs) was correlated to positive DVT to differentiate proximal DVT (above popliteal vein) from distal DVT (below popliteal vein).

RESULTS

Data of 1,909 patients were analyzed, and 239 (12.5%) patients were excluded secondary to serial repeat visits or follow-ups, surveillance screens, and if they had a previous history of DVT. The average age was 62.1 ± 16.3 years with more women (55.7%) and the majority presented with limb pain and edema (87%). DD studies were ordered and completed in 202 patients and correlated with all positive and negative DVT patients (100% sensitivity and negative predictive value, with specificity and positive predictive value of 14.9% and 15.9%, respectively). Twenty-six of 202 patients had DD that were in the normal range 0.1-0.59 mg/L (FEU), all of which were negative for DVT (100% sensitive). Fifty one of 202 patients had DD values of 0.6-1.2 mg/L FEU, of which only 3 DVTs were recorded, and all of them were distal DVTs. In addition, 685 patients with WCP <1 and negative DD were sent for VDU. Thus, 762 patients had an unnecessary immediate VDU (Wells ≤1 and -DD) study during their initial presentation. Potential charge savings for VDU for all patients are 762 × $1,557 = $1,186,434 and DD for all patients are 762 × $182 = $138,684, with total potential savings of $1,047,750 (USD 2016).

CONCLUSIONS

This study suggests that DD is still underutilized, and DD in conjunction with WCP could significantly reduce the number of unnecessary immediate VDUs. Higher value of DD (>1.2 mg/L FEU) may raise concern for proximal DVT. Concern on cost-effectiveness exists and raises the demand for a proposed algorithm to be followed.