Comparing PCSK9 Monoclonal Antibody Treatment Strategies Following Myocardial Infarction Using Negative Control Outcomes: A Target Trial Emulation Study

BACKGROUND

Initiation of proprotein convertase subtilisin/kexin type 9 monoclonal antibody (PCSK9 mAb) for lipid-lowering following myocardial infarction (MI) is likely affected by patients' prognostic factors, potentially leading to bias when comparing real-world treatment effects.

METHODS

Using target-trial emulation, we assessed potential confounding when comparing two treatment strategies post-MI: initiation of PCSK9 mAb within 1 year and no initiation of PCSK9 mAb. We identified MI hospitalizations during July 2015-June 2020 for patients aged ≥18 years in Optum's de-identified Clinformatics® Data Mart (CDM) and MarketScan, and aged ≥66 in US Medicare claims database. We estimated 3-year counterfactual cumulative risk and risk difference (RD) for 10 negative control outcomes using the clone-censor-weight approach to address time-varying confounding and immortal person-time.

RESULTS

PCSK9 mAb initiation within 1-year post-MI was low (0.7% in MarketScan and 0.4% in both CDM and Medicare databases). In CDM, there was a lower risk for cancer (RD = -3.6% [95% CI: -4.3%, -2.9%]), decubitus ulcer (RD = -7.7% [95% CI: -11.8%, -3.7%]), fracture (RD = -8.1% [95% CI: -9.6%, -6.6%]), influenza vaccine (RD = -9.3% [95% CI: -17.5%, -1.1%]), and visual test (RD = -0.6% [95% CI: -0.7%, -0.6%]) under the PCSK9 mAb initiation vs. no initiation strategy. Similar differences persisted in the MarketScan and Medicare databases. In each database, ezetimibe and low-density lipoprotein testing were unbalanced between treatment strategies.

CONCLUSION

A comparative effectiveness study of these treatments using the current approach would likely bias results due to the low number of PCSK9 mAb initiators.

Influence of Incomplete Death Information on Cumulative Risk Estimates in United States Claims Data

Administrative claims databases often do not capture date or fact of death, so studies using these data may inappropriately treat death as a censoring event-equivalent to other withdrawal reasons-rather than a competing event. We examined 1-, 3-, and 5-year inverse-probability-of-treatment-weighted cumulative risks of a composite cardiovascular outcome among 34,527 initiators of telmisartan (exposure) and ramipril (referent) ages ≥55 in Optum claims from 2003 to 2020. Differences in cumulative risks of the cardiovascular endpoint due to censoring of death (cause-specific), as compared to treating death as a competing event (sub-distribution), increased with greater follow-up time and older age, where event and mortality risks were higher. Among ramipril users (selected results), 5-year cause-specific and sub-distribution cumulative risk estimates per 100, respectively, were 16.4 (95% CI 15.3, 17.5) and 16.2 (95% CI 15.1, 17.3) among ages 55-64 (difference=0.2) and were 43.2 (95% CI 41.3, 45.2) and 39.7 (95% CI 37.9, 41.4) among ages ≥75 (difference=3.6). Plasmode simulation results demonstrated the differences in cause-specific versus sub-distribution cumulative risks to increase with increasing mortality rate. We suggest researchers consider the cohort's baseline mortality risk when deciding whether real-world data with incomplete death information can be used without concern.

Staging and clean room: Constructs designed to facilitate transparency and reduce bias in comparative analyses of real-world data

PURPOSE

We describe constructs designed to protect the integrity of the results from comparative analyses using real-world data (RWD): staging and clean room.

METHODS

Staging involves performing sequential preliminary analyses and evaluating the population size available and potential bias before conducting comparative analyses. A clean room involves restricted access to data and preliminary results, policies governing exploratory analyses and protocol deviations, and audit trail. These constructs are intended to allow decisions about protocol deviations, such as changes to design or model specification, to be made without knowledge of how they might affect subsequent analyses. We describe an example for implementing staging with a clean room.

RESULTS

Stage 1 may involve selecting a data source, developing and registering a protocol, establishing a clean room, and applying inclusion/exclusion criteria. Stage 2 may involve attempting to achieve covariate balance, often through propensity score models. Stage 3 may involve evaluating the presence of residual confounding using negative control outcomes. After each stage, check points may be implemented when a team of statisticians, epidemiologists and clinicians masked to how their decisions may affect study outcomes, reviews the results. This review team may be tasked with making recommendations for protocol deviations to address study precision or bias. They may recommend proceeding to the next stage, conducting additional analyses to address bias, or terminating the study. Stage 4 may involve conducting the comparative analyses.

CONCLUSIONS

The staging and clean room constructs are intended to protect the integrity and enhance confidence in the results of analyses of RWD.

Characterizing Imbalance in the Tails of the Propensity Score Distribution

Understanding characteristics of patients with propensity scores in the tails of the propensity score (PS) distribution has relevance for inverse-probability-of-treatment-weighted and PS-based estimation in observational studies. Here we outline a method for identifying variables most responsible for extreme propensity scores. The approach is illustrated in 3 scenarios: 1) a plasmode simulation of adult patients in the National Ambulatory Medical Care Survey (2011-2015) and 2) timing of dexamethasone initiation and 3) timing of remdesivir initiation in patients hospitalized for coronavirus disease 2019 from February 2020 through January 2021. PS models were fitted using relevant baseline covariates, and tails of the PS distribution were defined using asymmetric first and 99th percentiles. After fitting of the PS model in each original data set, values of each key covariate were permuted and model-agnostic variable importance measures were examined. Visualization and variable importance techniques were helpful in identifying variables most responsible for extreme propensity scores and may help identify individual characteristics that might make patients inappropriate for inclusion in a study (e.g., off-label use). Subsetting or restricting the study sample based on variables identified using this approach may help investigators avoid the need for trimming or overlap weights in studies.

Impact of the COVID-19 Pandemic on Pediatric Preventive Health Care Among North Carolina Children Enrolled in Medicaid

BACKGROUND

Children enrolled in private insurance had reduced preventive health care during the coronavirus disease 2019 (COVID-19) pandemic. However, the impact of the pandemic on children enrolled in Medicaid has been minimally described.

METHODS

We used an administrative claims database from North Carolina Medicaid to evaluate the rates of well-child visits and immunization administration for children ≤14 months of age, and used a quasi-Poisson regression model to estimate the rate ratio (RR) of each outcome during the pandemic period (3/15/2020 through 3/15/2021) compared with the pre-pandemic period (3/15/2019 through 3/14/2020).

RESULTS

We included 83 442 children during the pre-pandemic period and 96 634 children during the pandemic period. During the pre-pandemic period, 405 295 well-child visits and 715 100 immunization administrations were billed; during the pandemic period, 287 285 well-child visits and 457 144 immunization administrations were billed. The rates of well-child visits (RR 0.64; 95% CI, 0.64-0.64) and vaccine administration (RR 0.55; 95% CI, 0.55-0.55) were lower during the pandemic compared with the pre-pandemic period.

CONCLUSIONS

The rates of well-child visits and immunization administrations among North Carolina children enrolled in public insurance substantially decreased during the first year of the COVID-19 pandemic.

Trends in Pediatric Emergency and Inpatient Healthcare Use for Mental and Behavioral Health Among North Carolinians During the Early COVID-19 Pandemic

BACKGROUND

Widespread school closures and health care avoidance during the COVID-19 pandemic led to disruptions in access to pediatric mental health care.

METHODS

We conducted a retrospective study of emergency and inpatient administrative claims from privately insured children aged 6-20 years in North Carolina between January 2019 and December 2020. We compared rates of emergency department (ED) visits (per 100 000 person-days) and risks of hospitalizations (per 100 000 persons) with diagnosis codes in each category (mental/behavioral health; suicidal ideation, suicide attempt, and intentional self-harm [SI/SA/ISH]; and social issues) across 3 time periods (pre-pandemic, lockdown, and reopening). We calculated the proportion and 95% confidence intervals (CI) of total ED visits and total hospitalizations attributable to mental/behavioral health and SI/SA/ISH across the 3 time periods.

RESULTS

Rates of all categories of ED visits decreased from pre-pandemic to the lockdown period; from pre-pandemic to the reopening period, mental/behavioral health visits decreased but rates of SI/SA/ISH visits were unchanged. The proportion of ED visits attributable to mental/behavioral health increased from 3.5% (95% CI 3.2%-3.7%) pre-pandemic to 4.0% (95% CI 3.7%-4.3%) during reopening, and the proportion of SI/SA/ISH diagnoses increased from 1.6% (95% CI 1.4%-1.8%) pre-pandemic to 2.4% (95% CI 2.1%-2.7%) during the reopening period. Emergency care use for social issues and hospital admissions for mental/behavioral health and SI/SA/ISH diagnoses were unchanged across the study periods.

CONCLUSIONS

In the early pandemic, pediatric mental health care and acute suicidal crises accounted for increased proportions of emergency care. During pandemic recovery, understanding the populations most impacted and increasing access to preventative mental health care is critical.

Leveraging School Infection Data to Address Community COVID-19 Data Gaps

BACKGROUND

At-home COVID-19 tests became available in the USA in April 2021 with widespread use by January 2022; however, the lack of infrastructure to report test results to public health agencies created a gap in public health data. Kindergarten through grade 12 (K-12) schools often tracked COVID-19 cases among students and staff; leveraging school data may have helped bridge data gaps.

METHODS

We examined infection rates reported by school districts to ABC Science Collaborative with corresponding community rates from March 15, 2021 to June 3, 2022. We computed weekly ratios of community-to-district-reported rates (reporting ratios) across 3 study periods (spring 2021, fall 2021, and spring 2022) and estimated the difference and 95% confidence intervals (CIs) in the average reporting ratio between study periods.

RESULTS

In spring 2021, before approval or widespread use of at-home testing, the community-reported infection rate was higher than the school-reported infection rate (reporting ratio: 1.40). In fall 2021 and spring 2022, as at-home testing rapidly increased, school-reported rates were higher than community-reported rates (reporting ratios: 0.82 and 0.66). Average reporting ratios decreased between spring 2021 and fall 2021 (-0.58, 95% CI -0.84, -0.32) and spring 2021 and spring 2022 (-0.73, 95% CI -0.96, -0.48); there was no significant change between fall 2021 and spring 2022 (-0.15, 95% CI -0.36, 0.06).

CONCLUSIONS

At-home COVID-19 testing resulted in significant data gaps; K-12 data could have supplemented community data. In future public health emergencies, reporting of school data could minimize data gaps, but requires additional resources including funding to track infections and standardized data reporting methods.

Effects of Adjusting for Instrumental Variables on the Bias and Precision of Propensity Score Weighted Estimators: Analysis Under Complete, Near, and No Positivity Violations

Purpose

To demonstrate that using an instrumental variable (IV) with monotonicity reduces the accuracy of propensity score (PS) weighted estimators for the average treatment effect (ATE).

Methods

Monotonicity in the relationship between a binary IV and a binary treatment variable is an important assumption to identify the ATE for compliers who would only take treatment when encouraged by the IV. We perform theoretical and numerical investigations to study the impact of using the IV that satisfies monotonicity on the PS of treatment in terms of the positivity assumption, which requires that the PS be strictly between 0 and 1, and the accuracy of PS weighted estimators. Two versions of monotonicity that result in one-sided or two-sided noncompliance are considered.

Results

The PS adjusting for the IV always violates the positivity assumption when noncompliance occurs in one direction (one-sided noncompliance) and is more extreme than without the IV under two-sided noncompliance. These results are valid if the probability of being encouraged to get treatment and the compliance score, the probability of being a complier, are strictly between 0 and 1.

Conclusion

Using a binary IV with monotonicity as a covariate for the PS model makes the estimated PSs unnecessarily extreme, reducing the accuracy of the PS weighted estimators.

Propensity score methods in observational research: brief review and guide for authors

Causal inference in observational research requires a careful approach to adjustment for confounding. One such approach is the use of propensity score analyses. In this editorial, we focus on the role of propensity score-based methods in estimating causal effects from non-randomised observational data. We highlight the details, assumptions, and limitations of these methods and provide authors with guidelines for the conduct and reporting of propensity score analyses.

Cardiovascular Safety in Postmenopausal Women and Men With Osteoporosis Treated With Denosumab and Zoledronic Acid: A Post-Authorization Safety Study

Osteoporosis and cardiovascular disease are common in older adults. Treatment of osteoporosis reduces the burden of debilitating fractures; however, it is important to understand the benefit versus risk of treatment. This study evaluates the risk of stroke (ischemic or hemorrhagic) and myocardial infarction (MI) among postmenopausal women and men initiating osteoporosis treatment with denosumab (receptor activator of nuclear factor κB ligand [RANKL] inhibitor) or zoledronic acid (bisphosphonate) between October 2010 and June 2019. A retrospective cohort study employing the new user/active comparator design was conducted. Analyses were conducted separately in two national US commercial databases, MarketScan® and Optum® for reproducibility. Inverse probability of treatment and censoring weighting was employed to control for confounding and informative censoring. Cumulative risks at 6-month, 12-month, and 36-month time points were calculated and adjusted risk ratios and differences (with 95% confidence intervals [CIs]) were estimated. In MarketScan® and Optum® databases, 96,611 and 73,127 patients met all study eligibility criteria, respectively. At 36 months, the risk ratio estimates (zoledronic acid referent group) were 1.22 (95% CI, 0.77-1.66) and 0.97 (95% CI, 0.63-1.32) for MI and 1.00 (95% CI, 0.61-1.40) and 0.87 (95% CI, 0.56-1.17) for stroke in MarketScan and Optum, respectively. Most of the treatment associations across the other time periods and outcomes also had 95% CIs including the null value. In these large samples of real-world US patients, no increased risk in MI and stroke were identified for up to 36 months of treatment in denosumab users compared with zoledronic acid users. © 2023 Amgen. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

G-estimation of structural nested mean models for interval-censored data using pseudo-observations

Two large-scale randomized clinical trials compared fenofibrate and placebo in diabetic patients with pre-existing retinopathy (FIELD study) or risk factors (ACCORD trial) on an intention-to-treat basis and reported a significant reduction in the progression of diabetic retinopathy in the fenofibrate arms. However, their analyses involved complications due to intercurrent events, that is, treatment-switching and interval-censoring. This article addresses these problems involved in estimation of causal effects of long-term use of fibrates in a cohort study that followed patients with type 2 diabetes for 8 years. We propose structural nested mean models (SNMMs) of time-varying treatment effects and pseudo-observation estimators for interval-censored data. The first estimator for SNMMs uses a nonparametric maximum likelihood estimator (MLE) as a pseudo-observation, while the second estimator is based on MLE under a parametric piecewise exponential distribution. Through numerical studies with real and simulated datasets, the pseudo-observations estimators of causal effects using the nonparametric Wellner-Zhan estimator perform well even under dependent interval-censoring. Its application to the diabetes study revealed that the use of fibrates in the first 4 years reduced the risk of diabetic retinopathy but did not support its efficacy beyond 4 years.

Epidemiology of Community-Acquired Acute Kidney Injury Among US Veterans

RATIONALE & OBJECTIVE

Community-acquired acute kidney injury (CA-AKI) develops outside of the hospital and is the most common form of AKI globally. National estimates of CA-AKI in the United States are absent due to limited availability of laboratory data. This study leverages national data from the Veterans Health Administration (VA) to estimate incidence and risk factors of CA-AKI.

STUDY DESIGN

Retrospective cohort study using national VA administrative and laboratory data to assess cumulative CA-AKI incidence.

SETTING & PARTICIPANTS

VA primary care patients in 2013-2017 with recorded outpatient serum creatinine (Scr) and no history of chronic kidney disease≥stage 5.

PREDICTOR

Sociodemographics, comorbidities, medication use, and health care utilization.

OUTCOME

Annual incidence of CA-AKI defined as a≥1.5-fold relative increase in Scr on either a subsequent outpatient Scr or inpatient Scr obtained within ≤24 hours of admission.

ANALYTICAL APPROACH

We calculated the relative change in Scr within 12 months of an outpatient Scr value. A Cox model was used to estimate the association between CA-AKI and baseline characteristics, accounting for repeated measurements.

RESULTS

Of approximately 2.5 million eligible veterans each year, the cumulative incidence of CA-AKI was approximately 2% annually. Only 27% of CA-AKI was detected at hospital admission. In adjusted analyses, high health care utilization, chronic illness, cancer, rural location, female sex, and use of renin-angiotensin aldosterone system inhibitors or diuretics were associated with increased CA-AKI risk (all, HR>1.20).

LIMITATIONS

Limited generalizability of results outside a veteran population, lack of a standardized definition for CA-AKI, and possibility of surveillance bias and misclassification.

CONCLUSIONS

CA-AKI affects 1 of every 50 US veterans annually. With less than a third of CA-AKI observed in the inpatient hospital setting, reliance on inpatient evaluation of AKI suggests significant underrecognition and missed opportunities to prevent and manage the long-term consequences of AKI.

In-Person Instruction and Educational Outcomes of K-8 Students During the COVID-19 Pandemic

OBJECTIVES

Quantify the relationship between district policy permitting in-person instruction and educational outcomes during the 2020 to 2021 academic year for kindergarten through eighth grade students.

METHODS

An ecological, repeated cross-sectional analysis of grade-level proficiency of students enrolled in public school districts in North Carolina (n = 115 school districts) was conducted. Univariate and multivariate analyses were performed to evaluate the association between the proportion of the school year a district spent in-person and 2020 to 2021 end-of-year student proficiency in the district. We then fit a multivariable linear regression model, weighted by district size, and adjusted for district-level 2018 to 2019 proficiency and district-level factors (rural or urban, area deprivation).

RESULTS

Compared to 2018 to 2019, there was a 12.1% decrease (95% confidence interval [CI]: 16.8-19.3) in mathematics and an 18.1% decrease (95% CI: 10.8-13.4) in reading proficiency across the state at the end of 2020 to 2021. Compared to a district that remained entirely remote for the 2020 to 2021 school year, a district offering full in-person instruction had 12% (95% CI: 11%-12.9%) and 4.1% (95% CI: 3.5%-4.8%) more students achieve grade-level proficiency in mathematics and reading, respectively. In-person instruction was associated with greater increases in mathematics proficiency than reading, and greater increases in elementary-level students' proficiency than middle school-level.

CONCLUSIONS

The proportion of students achieving grade-level proficiency in 2020 to 2021 fell below prepandemic levels at each evaluated time point in the academic year. Increased time spent in-person by a school district was associated with an increased proportion of students achieving grade-level end-of-grade proficiency in both mathematics and reading.

Utilization and Impact of Symptomatic and Exposure SARS-CoV-2 Testing in K-12 Schools

OBJECTIVES

The Centers for Disease Control and Prevention recommend that schools can offer severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) diagnostic (on-demand) testing for students and staff with coronavirus disease 2019 symptoms or exposures. Data related to the uptake, implementation, and effect of school-associated on-demand diagnostic testing have not been described.

METHODS

The Rapid Acceleration of Diagnostics Underserved Populations Return to School program provided resources to researchers to implement on-demand SARS-CoV-2 testing in schools. This study describes the strategies used and uptake among the different testing programs. Risk of positivity was compared for symptomatic and exposure testing during the δ and ο variant periods. We estimated the number of school absence days saved with school-based diagnostic testing.

RESULTS

Of the 16 eligible programs, 7 provided school-based on-demand testing. The number of persons that participated in these testing programs is 8281, with 4134 (49.9%) receiving >1 test during the school year. Risk of positivity was higher for symptomatic testing compared with exposure testing and higher during the ο variant predominant period compared with the δ variant predominant period. Overall, access to testing saved an estimated 13 806 absent school days.

CONCLUSIONS

School-based on-demand SARS-CoV-2 testing was used throughout the school year, and nearly half the participants accessed testing on more than 1 occasion. Future studies should work to understand participant preferences around school-based testing and how these strategies can be used both during and outside of pandemics.

Building School-Academic Partnerships to Implement COVID-19 Testing in Underserved Populations

OBJECTIVE

In April 2021, the US government made substantial investments in students' safe return to school by providing resources for school-based coronavirus disease 2019 (COVID-19) mitigation strategies, including COVID-19 diagnostic testing. However, testing uptake and access among vulnerable children and children with medical complexities remained unclear.

METHODS

The Rapid Acceleration of Diagnostics Underserved Populations program was established by the National Institutes of Health to implement and evaluate COVID-19 testing programs in underserved populations. Researchers partnered with schools to implement COVID-19 testing programs. The authors of this study evaluated COVID-19 testing program implementation and enrollment and sought to determine key implementation strategies. A modified Nominal Group Technique was used to survey program leads to identify and rank testing strategies to provide a consensus of high-priority strategies for infectious disease testing in schools for vulnerable children and children with medical complexities.

RESULTS

Among the 11 programs responding to the survey, 4 (36%) included prekindergarten and early care education, 8 (73%) worked with socioeconomically disadvantaged populations, and 4 focused on children with developmental disabilities. A total of 81 916 COVID-19 tests were performed. "Adapting testing strategies to meet the needs, preferences, and changing guidelines," "holding regular meetings with school leadership and staff," and "assessing and responding to community needs" were identified as key implementation strategies by program leads.

CONCLUSIONS

School-academic partnerships helped provide COVID-19 testing in vulnerable children and children with medical complexities using approaches that met the needs of these populations. Additional work is needed to develop best practices for in-school infectious disease testing in all children.

A Per-Protocol Analysis Using Inverse-Probability-of-Censoring Weights in a Randomized Trial of Initial Protease Inhibitor Versus Nonnucleoside Reverse Transcriptase Inhibitor Regimens in Children

Protocol adherence may influence measured treatment effectiveness in randomized controlled trials. Using data from a multicenter trial (Europe and the Americas, 2002-2009) of children with human immunodeficiency virus type 1 who had been randomized to receive initial protease inhibitor (PI) versus nonnucleoside reverse transcriptase inhibitor (NNRTI) antiretroviral therapy regimens, we generated time-to-event intention-to-treat (ITT) estimates of treatment effectiveness, applied inverse-probability-of-censoring weights to generate per-protocol efficacy estimates, and compared shifts from ITT to per-protocol estimates across and within treatment arms. In ITT analyses, 263 participants experienced 4-year treatment failure probabilities of 41.3% for PIs and 39.5% for NNRTIs (risk difference = 1.8% (95% confidence interval (CI): -10.1, 13.7); hazard ratio = 1.09 (95% CI: 0.74, 1.60)). In per-protocol analyses, failure probabilities were 35.6% for PIs and 29.2% for NNRTIs (risk difference = 6.4% (95% CI: -6.7, 19.4); hazard ratio = 1.30 (95% CI: 0.80, 2.12)). Within-arm shifts in failure probabilities from ITT to per-protocol analyses were 5.7% for PIs and 10.3% for NNRTIs. Protocol nonadherence was nondifferential across arms, suggesting that possibly better NNRTI efficacy may have been masked by differences in within-arm shifts deriving from differential regimen forgiveness, residual confounding, or chance. A per-protocol approach using inverse-probability-of-censoring weights facilitated evaluation of relationships among adherence, efficacy, and forgiveness applicable to pediatric oral antiretroviral regimens.

Controlling for Differential Regression-To-The-Mean via Propensity Scores: A Simulation Study

Purpose

Regression-to-the-mean (RTM) is a statistical phenomenon that may occur in epidemiologic studies where inclusion in the study cohort is contingent upon experiencing a laboratory/clinical measurement beyond a defined threshold. When differential across treatment groups, RTM could bias the final study estimate. This poses substantial challenges in observational studies that index patients upon experiencing extreme laboratory or clinical values. Our objective was to investigate propensity score-based methods as a tool for mitigating this source of bias via simulation.

Methods

We simulated a noninterventional comparative effectiveness study, comparing treatment with romiplostim to standard-of-care therapies for immune thrombocytopenia (ITP), a disease characterized by low platelet counts. Platelet counts were generated from normal distributions according to the underlying ITP severity, a strong confounder of treatment and outcome. Patients were assigned treatment probabilities based upon ITP severity, which created varied levels of differential and non-differential RTM. Treatments were compared via the difference in median platelet counts during 23 weeks of follow-up. We calculated four summary metrics of the platelet counts measured prior to cohort entry and built six propensity score models to adjust for those variables. We adjusted for these summary metrics using inverse probability of treatment weights.

Results

Across all simulated scenarios, propensity score adjustment reduced bias and increased precision of the treatment effect estimator. Adjusting for combinations of the summary metrics was most effective at reducing bias. Adjusting for the mean of prior platelet counts or the difference between the cohort-qualifying platelet count and the largest prior count eliminated the most bias when assessed individually.

Conclusion

These results suggest that differential RTM could be reasonably addressed by propensity score models with summaries of historical laboratory values. This approach can be easily applied to any comparative effectiveness or safety study, though investigators should carefully consider the best summary metric for their data.

Effectiveness of Remdesivir Treatment Protocols Among Patients Hospitalized with COVID-19: A Target Trial Emulation

BACKGROUND

Remdesivir is recommended for certain hospitalized patients with COVID-19. However, these recommendations are based on evidence from small randomized trials, early observational studies, or expert opinion. Further investigation is needed to better inform treatment guidelines with regard to the effectiveness of remdesivir among these patients.

METHODS

We emulated a randomized target trial using chargemaster data from 333 US hospitals from 1 May 2020 to 31 December 2021. We compared three treatment protocols: remdesivir within 2 days of hospital admission, no remdesivir within the first 2 days of admission, and no remdesivir ever. We used baseline comorbidities recorded from encounters up to 12 months before admission and identified the use of in-hospital medications, procedures, and oxygen supplementation from charges. We estimated the cumulative incidence of mortality or mechanical ventilation/extracorporeal membrane oxygenation with an inverse probability of censoring weighted estimator. We conducted analyses in the total population as well as in subgroups stratified by level of oxygen supplementation.

RESULTS

A total of 274,319 adult patients met the eligibility criteria for the study. Thirty-day in-hospital mortality risk differences for patients adhering to the early remdesivir protocol were -3.1% (95% confidence interval = -3.5%, -2.7%) compared to no early remdesivir and -3.7% (95% confidence interval -4.2%, -3.2%) compared to never remdesivir, with the strongest effect in patients needing high-flow oxygen. For mechanical ventilation/extracorporeal membrane oxygenation, risk differences were minimal.

CONCLUSIONS

We estimate that, among hospitalized patients with COVID-19, remdesivir treatment within 2 days of admission reduced 30-day in-hospital mortality, particularly for patients receiving supplemental oxygen on the day of admission.

Test-to-Stay in Kindergarten Through 12th Grade Schools After Household Exposure to Severe Acute Respiratory Syndrome Coronavirus 2

BACKGROUND

Test-to-stay (TTS) is a strategy to limit school exclusion following an exposure to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). We evaluated the use of TTS within universally masked kindergarten through 12th grade (K-12) school settings following household SARS-CoV-2 exposure.

METHODS

Three hundred twenty-two participants were enrolled. Serial rapid antigen testing was performed up to 15 days post-exposure. Analysis-eligible participants completed the 15-day testing protocol, tested positive any time during the testing window, or received a negative test on or after day 9. Primary outcomes included within-school tertiary attack rate (TAR) (test positivity among close contacts of positive TTS participants), and school days saved among TTS participants.

RESULTS

Seventy-three of 265 analysis-eligible participants tested positive for SARS-CoV-2 (secondary attack rate of 28% [95% CI: 16-63%]). Among 77 within-school close contacts, 2 were positive (TAR = 3% [95% CI: 1-5%]). Participant absences were limited to 338 days, resulting in 82% of 1849 school days saved.

IMPLICATIONS FOR SCHOOL HEALTH POLICY, PRACTICE, AND EQUITY

TTS facilitates continued in-person learning and can greatly reduce the number of missed school days.

CONCLUSIONS

Within universally masked K-12 schools, TTS is a safe alternative to school exclusion following household SARS-CoV-2 exposure.

Pragmatic considerations for negative control outcome studies to guide non-randomized comparative analyses: A narrative review

This narrative review describes the application of negative control outcome (NCO) methods to assess potential bias due to unmeasured or mismeasured confounders in non-randomized comparisons of drug effectiveness and safety. An NCO is assumed to have no causal relationship with a treatment under study while subject to the same confounding structure as the treatment and outcome of interest; an association between treatment and NCO then reflects the potential for uncontrolled confounding between treatment and outcome. We focus on two recently completed NCO studies that assessed the comparability of outcome risk for patients initiating different osteoporosis medications and lipid-lowering therapies, illustrating several ways in which confounding may result. In these studies, NCO methods were implemented in claims-based data sources, with the results used to guide the decision to proceed with comparative effectiveness or safety analyses. Based on this research, we provide recommendations for future NCO studies, including considerations for the identification of confounding mechanisms in the target patient population, the selection of NCOs expected to satisfy required assumptions, the interpretation of NCO effect estimates, and the mitigation of uncontrolled confounding detected in NCO analyses. We propose the use of NCO studies prior to initiating comparative effectiveness or safety research, providing information on the potential presence of uncontrolled confounding in those comparative analyses. Given the increasing use of non-randomized designs for regulatory decision-making, the application of NCO methods will strengthen study design, analysis, and interpretation of real-world data and the credibility of the resulting real-world evidence. This article is protected by copyright. All rights reserved.

External Comparator Groups Derived from Real-world Data Used in Support of Regulatory Decision Making: Use Cases and Challenges

Real-world data (RWD) from electronic health records (EHRs) and administrative claims databases are used increasingly to generate real-world evidence (RWE). RWE is used to support clinical evidence packages for medicines that inform decision-makers. In this review of current issues in the use of RWD-derived external comparator groups to support regulatory filings, we assess a series of topics that generally apply across many disease indications. However, most of the examples and illustrations focus on the oncology clinical research setting. The topics include an overview of current uses of RWD in drug development, a discussion of regulatory filings using RWD-derived external comparators, a brief overview of guidance documents and white papers pertaining to external comparators, a summary of some limitations and methodological issues in the use of external comparator groups and finally, a look at the future of this area and recommendations.

Visualizations throughout pharmacoepidemiology study planning, implementation, and reporting

Transparency is increasingly promoted to instill trust in nonrandomized studies using real-world data. Graphics and data visualizations support transparency by aiding communication and understanding, and can inform study design and analysis decisions. However, other than graphical representation of a study design and flow diagrams (e.g., a Consolidated Standards of Reporting Trials [CONSORT] like diagram), specific standards on how to maximize validity and transparency with visualization are needed. This paper provides guidance on how to use visualizations throughout the life cycle of a pharmacoepidemiology study-from initial study design to final report-to facilitate rationalized and transparent decision-making about study design and implementation, and clear communication of study findings. Our intent is to help researchers align their practices with current consensus statements on transparency.

Test-to-Stay After SARS-CoV-2 Exposure: A Mitigation Strategy for Optionally Masked K-12 Schools

OBJECTIVES

We evaluated the impact of a test-to-stay (TTS) program on within-school transmission and missed school days in optionally masked kindergarten through 12th grade schools during a period of high community severe acute respiratory syndrome coronavirus 2 transmission.

METHODS

Close contacts of those with confirmed severe acute respiratory syndrome coronavirus 2 infection were eligible for enrollment in the TTS program if exposure to a nonhousehold contact occurred between November 11, 2021 and January 28, 2022. Consented participants avoided school exclusion if they remained asymptomatic and rapid antigen testing at prespecified intervals remained negative. Primary outcomes included within-school tertiary attack rate (test positivity among close contacts of positive TTS participants) and school days saved among TTS participants. We estimated the number of additional school-acquired cases resulting from TTS and eliminating school exclusion.

RESULTS

A total of 1675 participants tested positive or received at least 1 negative test between days 5 and 7 and completed follow-up; 92% were students and 91% were exposed to an unmasked primary case. We identified 201 positive cases. We observed a tertiary attack rate of 10% (95% confidence interval: 6%-19%), and 7272 (89%) of potentially missed days were saved through TTS implementation. We estimated 1 additional school-acquired case for every 21 TTS participants remaining in school buildings during the entire study period.

CONCLUSIONS

Even in the setting of high community transmission, a TTS strategy resulted in substantial reduction in missed school days in optionally masked schools.

Azithromycin use increases the risk of sudden cardiac death in patients with hemodialysis-dependent kidney failure

Azithromycin is an antibiotic with QT-prolonging potential commonly prescribed to individuals receiving hemodialysis. Hemodialysis patients have a high prevalence of clinical conditions, such as structural heart disease, that can enhance the pro-arrhythmic effects azithromycin, but were excluded from prior investigations evaluating the cardiac safety of azithromycin. Using data from the United States Renal Data System (2007-2017), we conducted two cohort studies to examine the cardiac safety of azithromycin relative to amoxicillin-based antibiotics (amoxicillin, amoxicillin/clavulanic acid) and levofloxacin (a fluoroquinolone antibiotic known to prolong the QT-interval) in the hemodialysis population. The primary outcome was five-day sudden cardiac death. Using inverse probability of treatment weighted survival models, we estimated hazard ratios, risk differences, and 95% confidence intervals. The azithromycin vs. amoxicillin-based antibiotic cohort included 282,899 patients and 725,431 treatment episodes (381,306 azithromycin and 344,125 amoxicillin-based episodes). Azithromycin vs. amoxicillin-based antibiotic treatment was associated with higher relative and absolute risks of sudden cardiac death, weighted hazard ratio of 1.70 (95% Confidence Interval, 1.36 to 2.11) and weighted risk difference per 100,000 treatment episodes of 25.0 (15.5 to 36.5). The azithromycin vs. levofloxacin cohort included 245,143 patients and 554,557 treatment episodes (387,382 azithromycin and 167,175 levofloxacin episodes). Azithromycin vs. levofloxacin treatment was associated with lower relative and absolute risks of sudden cardiac death, weighted hazard ratio of 0.79 (0.64 to 0.96) and weighted risk difference per 100,000 treatment episodes of -18.9 (-35.5 to -3.8). Thus, when selecting among azithromycin, levofloxacin, and amoxicillin-based antibiotics, clinicians should weigh the relative antimicrobial benefits of these drugs against their potential cardiac risks.

The modifying effect of the serum-to-dialysate potassium gradient on the cardiovascular safety of SSRIs in the hemodialysis population: a pharmacoepidemiologic study

BACKGROUND

Hypokalemia is a risk factor for drug-induced QT-prolongation. Larger serum-to-dialysate potassium gradients during hemodialysis may augment the proarrhythmic risks of selective serotonin reuptake inhibitors (SSRIs).

METHODS

We conducted a cohort study using 2007-2017 data from the United States Renal Data System and a large dialysis provider to examine if the serum-to-dialysate potassium gradient modifies SSRI cardiac safety. Using a new-user design, we compared 1-year sudden cardiac death (SCD) risk among hemodialysis patients newly treated with higher (citalopram, escitalopram) vs. lower (fluoxetine, fluvoxamine, paroxetine, sertraline) QT-prolonging potential SSRIs, overall and stratified by baseline potassium gradient (≥4 vs. <4 mEq/L). We used inverse probability of treatment weighted survival models to estimate weighted hazard ratios (HRs) and 95% confidence intervals (CIs), and conducted a confirmatory nested case-control study.

RESULTS

The study included 25,099 patients: 11,107 (44.3%) higher QT-prolonging potential SSRI new-users and 13,992 (55.7%) lower QT-prolonging potential SSRI new-users. Overall, higher vs. lower QT-prolonging potential SSRI use was not associated with SCD, weighted HR of 1.03 (95% CI, 0.86-1.24). However, a greater risk of SCD was associated with higher vs. lower QT-prolonging potential SSRI use among patients with baseline potassium gradients ≥4 mEq/L, but not among those with gradients <4 mEq/L, weighted HR of 2.17 (95% CI, 1.16-4.03) vs. 0.95 (0.78-1.16). Nested case-control analyses yielded analogous results.

CONCLUSIONS

The serum-to-dialysate potassium gradient may modify the association between higher vs. lower QT-prolonging SSRI use and SCD among people receiving hemodialysis. Minimizing the potassium gradient in the setting of QT-prolonging medication use may be warranted.

School Masking Policies and Secondary SARS-CoV-2 Transmission

OBJECTIVES

Throughout the COVID-19 pandemic, masking has been a widely used mitigation practice in kindergarten through 12th grade (K-12) school districts to limit within-school transmission. Prior studies attempting to quantify the impact of masking have assessed total cases within schools; however, the metric that more optimally defines effectiveness of mitigation practices is within-school transmission, or secondary cases. We estimated the impact of various masking practices on secondary transmission in a cohort of K-12 schools.

METHODS

We performed a multistate, prospective, observational, open cohort study from July 26, 2021 to December 13, 2021. Districts reported mitigation practices and weekly infection data. Districts that were able to perform contact tracing and adjudicate primary and secondary infections were eligible for inclusion. To estimate the impact of masking on secondary transmission, we used a quasi-Poisson regression model.

RESULTS

A total of 1 112 899 students and 157 069 staff attended 61 K-12 districts across 9 states that met inclusion criteria. The districts reported 40 601 primary and 3085 secondary infections. Six districts had optional masking policies, 9 had partial masking policies, and 46 had universal masking. In unadjusted analysis, districts that optionally masked throughout the study period had 3.6 times the rate of secondary transmission as universally masked districts; and for every 100 community-acquired cases, universally masked districts had 7.3 predicted secondary infections, whereas optionally masked districts had 26.4.

CONCLUSIONS

Secondary transmission across the cohort was modest (<10% of total infections) and universal masking was associated with reduced secondary transmission compared with optional masking.

Lipid Testing Trends Before and After Hospitalization for Myocardial Infarction Among Adults in the United States, 2008-2019

Background

Routine monitoring of low-density lipoprotein cholesterol (LDL-C) identifies patients who may benefit from modifying lipid-lowering therapies (LLT). However, the extent to which LDL-C testing is occurring in clinical practice is unclear, specifically among patients hospitalized for a myocardial infarction (MI).

Methods

Using US commercial claims data, we identified patients with an incident MI hospitalization between 01/01/2008-03/31/2019. LDL-C testing was assessed in the year before admission (pre-MI) and the year after discharge (post-MI). Changes in LDL-C testing were evaluated using a Poisson model fit to pre-MI rates and extrapolated to the post-MI period. We predicted LDL-C testing rates if no MI had occurred (ie, based on pre-MI trends) and estimated rate differences and ratios (contrasting observed vs predicted rates).

Results

Overall, 389,367 patients were hospitalized for their first MI during the study period. In the month following discharge, 9% received LDL-C testing, increasing to 27% at 3 months and 52% at 12 months. Mean rates (tests per 1000 patients per month) in the pre- and post-MI periods were 51.9 (95% CI: 51.7, 52.1) and 84.4 (95% CI: 84.1, 84.6), respectively. Over 12 months post-MI, observed rates were higher than predicted rates; the maximum rate difference was 66 tests per 1000 patients in month 2 (rate ratio 2.2), stabilizing at a difference of 15-20 (ratio 1.2-1.3) for months 6-12.

Conclusion

Although LDL-C testing increased following MI hospitalization, rates remained lower than recommended by clinical guidelines. This highlights a potential gap in care, where increased LDL-C testing after MI may provide opportunities for LLT modification and decrease risk of subsequent cardiovascular events.

Proton pump inhibitors may enhance the risk of citalopram- and escitalopram-associated sudden cardiac death among patients receiving hemodialysis

PURPOSE

Polypharmacy is common in the hemodialysis population and increases the likelihood that patients will be exposed to clinically significant drug-drug interactions. Concurrent use of proton pump inhibitors (PPIs) with citalopram or escitalopram may potentiate the QT-prolonging effects of these selective serotonin reuptake inhibitors through pharmacodynamic and/or pharmacokinetic interactions.

METHODS

We conducted a retrospective cohort study using data from the U.S. Renal Data System (2007-2017) and a new-user design to examine the differential risk of sudden cardiac death (SCD) associated with citalopram/escitalopram initiation vs. sertraline initiation in the presence and absence of PPI use among adults receiving hemodialysis. We studied 72 559 patients:14 983 (21%) citalopram/escitalopram initiators using a PPI; 26 503 (36%) citalopram/escitalopram initiators not using a PPI;10 779 (15%) sertraline initiators using a PPI; and 20 294 (28%) sertraline initiators not using a PPI (referent). The outcome of interest was 1-year SCD. We used inverse probability of treatment weighted survival models to estimate weighted hazard ratios (HRs) and 95% confidence intervals (CIs).

RESULTS

Compared with sertraline initiators not using a PPI, citalopram/escitalopram initiators using a PPI had the numerically highest risk of SCD (HR [95% CI] = 1.31 [1.11-1.54]), followed by citalopram/escitalopram initiators not using a PPI (HR [95% CI] = 1.22 [1.06-1.41]). Sertraline initiators using a PPI had a similar risk of SCD compared with those not using a PPI (HR [95% CI] = 1.03 [0.85-1.26]).

CONCLUSIONS

Existing PPI use may elevate the risk of SCD associated with citalopram or escitalopram initiation among hemodialysis patients.

Approaches to Selecting "Time Zero" in External Control Arms with Multiple Potential Entry Points: A Simulation Study of 8 Approaches

BACKGROUND

When including data from an external control arm to estimate comparative effectiveness, there is a methodological choice of when to set "time zero," the point at which a patient would be eligible/enrolled in a contemporary study. Where patients receive multiple lines of eligible therapy and thus alternative points could be selected, this issue is complex.

METHODS

A simulation study was conducted in which patients received multiple prior lines of therapy before entering either cohort. The results from the control and intervention data sets are compared using 8 methods for selecting time zero. The base-case comparison was set up to be biased against the intervention (which is generally received later), with methods compared in their ability to estimate the true intervention effectiveness. We further investigate the impact of key study attributes (such as sample size) and degree of overlap in time-varying covariates (such as prior lines of therapy) on study results.

RESULTS

Of the 8 methods, 5 (all lines, random line, systematically selecting groups based on mean absolute error, root mean square error, or propensity scores) showed good performance in accounting for differences between the line at which patients were included. The first eligible line can be statistically inefficient in some situations. All lines (with censoring) cannot be used for survival outcomes. The last eligible line cannot be recommended.

CONCLUSIONS

Multiple methods are available for selecting the most appropriate time zero from an external control arm. Based on the simulation, we demonstrate that some methods frequently perform poorly, with several viable methods remaining. In selecting between the viable methods, analysts should consider the context of their analysis and justify the approach selected.

HIGHLIGHTS

There are multiple methods available from which an analyst may select "time zero" in an external control cohort.This simulation study demonstrates that some methods perform poorly but most are viable options, depending on context and the degree of overlap in time zero across cohorts.Careful thought and clear justification should be used when selecting the strategy for a study.

Test-to-Stay After Exposure to SARS-CoV-2 in K-12 Schools

OBJECTIVES

We evaluated the safety and efficacy of a test-to-stay program for unvaccinated students and staff who experienced an unmasked, in-school exposure to someone with confirmed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Serial testing instead of quarantine was offered to asymptomatic contacts. We measured secondary and tertiary transmission rates within participating schools and in-school days preserved for participants.

METHODS

Participating staff or students from universally masked districts in North Carolina underwent rapid antigen testing at set intervals up to 7 days after known exposure. Collected data included location or setting of exposure, participant symptoms, and school absences up to 14 days after enrollment. Outcomes included tertiary transmission, secondary transmission, and school days saved among test-to-stay participants. A prespecified interim safety analysis occurred after 1 month of enrollment.

RESULTS

We enrolled 367 participants and completed 14-day follow-up on all participants for this analysis. Nearly all (215 of 238, 90%) exposure encounters involved an unmasked index case and an unmasked close contact, with most (353 of 366, 96%) occurring indoors, during lunch (137 of 357, 39%) or athletics (45 of 357, 13%). Secondary attack rate was 1.7% (95% confidence interval: 0.6%-4.7%) based on 883 SARS-CoV-2 serial rapid antigen tests with results from 357 participants; no tertiary cases were identified, and 1628 (92%) school days were saved through test-to-stay program implementation out of 1764 days potentially missed.

CONCLUSION

After unmasked in-school exposure to SARS-CoV-2, even in a mostly unvaccinated population, a test-to-stay strategy is a safe alternative to quarantine.

Secondary Transmission of COVID-19 in K-12 Schools: Findings From 2 States

OBJECTIVES

We evaluated the impact of distancing practices on secondary transmission of severe acute respiratory syndrome coronavirus 2 and the degree of sports-associated secondary transmission across a large diverse cohort of schools during spring 2021.

METHODS

Participating districts in North Carolina and Wisconsin and North Carolina charter schools offering in-person instruction between March 15, 2021 and June 25, 2021 reported on distancing policies, community- and school-acquired infections, quarantines, and infections associated with school-sponsored sports. We calculated the ratio of school-acquired to community-acquired infection, secondary attack rates, and the proportion of secondary transmission events associated with sports. To estimate the effect of distancing and bus practices on student secondary transmission, we used a quasi-Poisson regression model with the number of primary student cases as the denominator.

RESULTS

During the study period, 1 102 039 students and staff attended in-person instruction in 100 North Carolina school districts, 13 Wisconsin school districts, and 14 North Carolina charter schools. Students and staff had 7865 primary infections, 386 secondary infections, and 48 313 quarantines. For every 20 community-acquired infections, there was 1 within-school transmission event. Secondary transmissions associated with school sports composed 46% of secondary transmission events in middle and high schools. Relaxed distancing practices (<3 ft, 3 ft) and increased children per bus seat were not associated with increased relative risk of secondary transmission.

CONCLUSIONS

With universal masking, in-person education was associated with low rates of secondary transmission, even with less stringent distancing and bus practices. Given the rates of sports-associated secondary transmission, additional mitigation may be warranted.

Urban Classification, Not COVID-19 Community Rates, Was Associated With Modes of Learning in US K-12 Schools?

OBJECTIVES

To identify factors associated with the decision to provide in-person, hybrid, and remote learning in kindergarten through 12th grade school districts during the 2020-2021 school year.

METHODS

We performed a retrospective study evaluating school district mode of learning and community coronavirus 2019 (COVID-19) incidence and percentage positivity rates at 3 time points during the pandemic: (1) September 15, 2020 (the beginning of the school year, before Centers for Disease Control and Prevention guidance); (2) November 15, 2020 (midsemester after the release of Centers for Disease Control and Prevention guidance and an increase of COVID-19 cases); and (3) January 15, 2021 (start of the second semester and peak COVID-19 rates). Five states were included in the analysis: Michigan, Missouri, North Carolina, Ohio, and Wisconsin. The primary outcome was mode of learning in elementary, middle, and high schools during 3 time points. The measures included community COVID-19 incidence and percentage positivity rates, school and student demographics, and county size classification of school location.

RESULTS

No relationship between mode of learning and community COVID-19 rates was observed. County urban classification of school location was associated with mode of learning with school districts in nonmetropolitan and small metropolitan counties more likely to be in-person.

CONCLUSIONS

Community COVID-19 rates did not appear to influence the decision of when to provide in-person learning. Further understanding of factors driving the decisions to bring children back into the classroom are needed. Standardizing policies on how schools apply national guidance to local decision-making may decrease disparities in emergent crises.

A School-Based SARS-CoV-2 Testing Program: Testing Uptake and Quarantine Length After In-School Exposures

OBJECTIVES

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-related quarantines, which are required after close contact with infected individuals, have substantially disrupted in-person education for kindergarten through 12th grade (K-12) students. In recent recommendations, shortened durations of quarantine are allowed if a negative SARS-CoV-2 test result is obtained at 5 to 7 days postexposure, but access to testing remains limited. We hypothesized that providing access to in-school SARS-CoV-2 testing postexposure would increase testing and reduce missed school days.

METHODS

This prospective cohort study was conducted in one large public K-12 school district in North Carolina and included 2 periods: preimplementation (March 15, 2021, to April 21, 2021) and postimplementation (April 22, 2021, to June 4, 2021), defined around initiation of an in-school SARS-CoV-2 testing program in which on-site access to testing is provided. Number of quarantined students and staff, testing uptake, test results, and number of missed school days were analyzed and compared between the preimplementation and postimplementation periods.

RESULTS

Twenty-four schools, including 12 251 in-person learners, participated in the study. During preimplementation, 446 close contacts were quarantined for school-related exposures; 708 close contacts were quarantined postimplementation. Testing uptake after school-related exposures increased from 6% to 40% (95% confidence interval: 23% to 45%) after implementation, and 89% of tests were conducted in-school. After in-school testing implementation, close contacts missed ∼1.5 fewer days of school (95% confidence interval: -2 to -1).

CONCLUSIONS

Providing access to in-school testing may be a worthwhile mechanism to increase testing uptake after in-school exposures and minimize missed days of in-person learning, thereby mitigating the pandemic's ongoing impact on children.

Masking Adherence in K-12 Schools and SARS-CoV-2 Secondary Transmission

OBJECTIVES

Masking is an essential coronavirus 2019 mitigation tool assisting in the safe return of kindergarten through 12th grade children and staff to in-person instruction; however, masking adherence, compliance evaluation methods, and potential consequences of surveillance are currently unknown. We describe 2 school districts' approaches to promote in-school masking and the consequent impact on severe acute respiratory syndrome coronavirus 2 secondary transmission.

METHODS

Two North Carolina school districts developed surveillance programs with daily versus weekly interventions to monitor in-school masking adherence. Safety teams recorded the proportion of students and staff appropriately wearing masks and provided real-time education after observation of improper masking. Primary infections, within-school transmission, and county-level severe acute respiratory syndrome coronavirus 2 infection rates were assessed.

RESULTS

Proper mask use was high in both intervention groups and districts. There were variations by grade level, with lower rates in elementary schools, and proper adherence being higher in the weekly surveillance group. Rates of secondary transmission were low in both districts with surveillance programs, regardless of intervention frequency.

CONCLUSIONS

Masking surveillance interventions are effective at ensuring appropriate masking at all school levels. Creating a culture of safety within schools led by local leadership is important and a feasible opportunity for school districts with return to in-person school. In our study of schools with high masking adherence, secondary transmission was low.

Use of negative control outcomes to assess the comparability of patients initiating lipid-lowering therapies

PURPOSE

Clinical trials have demonstrated efficacy of proprotein convertase subtilisin/kexin type 9 inhibitors (PCSK9i) in reducing risk of cardiovascular disease events, but effectiveness in routine clinical care has not been well-studied. We used negative control outcomes to assess potential confounding in an observational study of PCSK9i versus ezetimibe or high-intensity statin.

METHODS

Using commercial claims, we identified U.S. adults initiating PCSK9i, ezetimibe, or high-intensity statin in 2015-2018, with other lipid-lowering therapy (LLT) use in the year prior (LLT cohort) or atherosclerotic cardiovascular disease (ASCVD) in the past 90 days (ASCVD cohort). We compared initiators of PCSK9i to ezetimibe and high-intensity statin by estimating one-year risks of negative control outcomes influenced by frailty or health-seeking behaviors. Inverse probability of treatment and censoring weighted estimators of risk differences (RDs) were used to evaluate residual confounding after controlling for covariates.

RESULTS

PCSK9i initiators had lower one-year risks of negative control outcomes associated with frailty, such as decubitus ulcer in the ASCVD cohort (PCSK9i vs. high-intensity statin RD = -3.5%, 95% confidence interval (CI): -4.6%, -2.5%; PCSK9i vs. ezetimibe RD = -1.3%, 95% CI: -2.1%, -0.6%), with similar but attenuated associations in the LLT cohort. Lower risks of accidents and fractures were also observed for PCSK9i, varying by cohort. Risks were similar for outcomes associated with health-seeking behaviors, although trended higher for PCSK9i in the ASCVD cohort.

CONCLUSIONS

Observed associations suggest lower frailty and potentially greater health-seeking behaviors among PCSK9i initiators, particularly those with a recent ASCVD diagnosis, with the potential to bias real-world analyses of treatment effectiveness.

Analysis of Respiratory Fluoroquinolones and the Risk of Sudden Cardiac Death Among Patients Receiving Hemodialysis

Importance

Respiratory fluoroquinolone antibiotics are some of the most common medications with QT interval-prolonging potential prescribed to patients with hemodialysis-dependent kidney failure-individuals who have a very high risk of sudden cardiac death (SCD). To date, there have been no large-scale, population-specific studies evaluating the cardiac safety of respiratory fluoroquinolones in the hemodialysis population.

Objective

To investigate the cardiac safety of respiratory fluoroquinolones among individuals with hemodialysis-dependent kidney failure.

Design, Setting, and Participants

A retrospective cohort study examining safety using an active comparator new-user design was conducted using administrative claims data from a US-wide kidney failure registry from January 1, 2007, to December 31, 2016, including 264 968 Medicare beneficiaries receiving in-center maintenance hemodialysis. Data analysis was performed from January 4 to August 16, 2021.

Exposures

Respiratory fluoroquinolone (levofloxacin or moxifloxacin) vs amoxicillin-based (amoxicillin or amoxicillin with clavulanic acid) antibiotic treatment.

Main Outcomes and Measures

Sudden cardiac death within 5 days of outpatient initiation of a study antibiotic. Inverse probability of treatment-weighted survival models to estimate hazard ratios (HRs), risk differences (RDs), and corresponding 95% CIs. Death due to a cause other than SCD was treated as a competing event. Fracture was considered as a negative control outcome.

Results

The study cohort included 264 968 unique in-center hemodialysis patients and 626 322 study antibiotic treatment episodes: 251 726 respiratory fluoroquinolone treatment episodes (40.2%) and 374 596 amoxicillin-based treatment episodes (59.8%). Of the 264 968 patients, 135 236 (51.0%) were men, and the mean (SD) age was 61 (15) years. Respiratory fluoroquinolone vs amoxicillin-based antibiotic treatment was associated with a higher relative and absolute 5-day risk of SCD (weighted HR, 1.95; 95% CI, 1.57-2.41; and weighted RD per 100 000 treatment episodes, 44.0; 95% CI, 31.0-59.2). Respiratory fluoroquinolone vs amoxicillin-based antibiotic treatment was not associated with the 5-day risk of fracture.

Conclusions and Relevance

In this study, compared with amoxicillin-based antibiotic treatment, respiratory fluoroquinolone treatment was associated with a higher short-term risk of SCD among patients with hemodialysis-dependent kidney failure. This finding suggests that decisions between the use of respiratory fluoroquinolones and amoxicillin-based antibiotics should be individualized, with prescribers considering both the clinical benefits and potential cardiac risks.

Lipid testing trends before and after hospitalization for myocardial infarction among adults in the U.S., 2008–2019

Background

Routine monitoring of low-density lipoprotein cholesterol (LDL-C) identifies patients who are candidates for initiation of lipid-lowering therapies (LLT), assesses adherence and response, and measures clinical indications for modifications to treatment. This study investigated LDL-C testing trends among patients hospitalized for incident myocardial infarction (MI), a population at high risk of future atherosclerotic cardiovascular disease (ASCVD) events who may benefit from additional LLT.

Purpose

Our objective was to estimate rates of LDL-C testing before and after MI hospitalization, hypothesizing that testing rates would increase following MI.

Methods

Using claims data from a large population with Medicare supplemental or commercial insurance, we identified U.S. adults aged ≥20 years discharged from a MI hospitalization. Patients qualified for the study cohort if their first MI hospitalization occurred during 1/1/2008–3/31/2019, with one year of continuous enrolment in insurance leading up to the hospitalization. Patients were required to be discharged alive to the community (excluded if died or transferred to another facility). LDL-C testing was assessed in the year before admission (pre-MI) and for up to one year after discharge (post-MI), with censoring due to insurance plan disenrollment. To evaluate changes in LDL-C testing, we fit an overdispersed Poisson model to the time-series of pre-MI rates and extrapolated the model to the post-MI period, accounting for person-time and seasonality. We predicted the LDL-C testing rates if no MI occurred (i.e., based only on pre-MI testing trends) and estimated rate differences with 95% confidence intervals (contrasting observed vs. model-predicted rates).

Results

A total of 389,367 patients were hospitalized for their first MI during the study period with 60% aged &lt;65 years, 64% were male, and 51% filled a statin prescription after discharge (half being high-intensity statins). In the year pre-MI, 25% had a history of diabetes mellitus, 35% used statins, and 4% used ezetimibe. In the year post-MI, only 52% had an LDL-C test. Mean observed rates (tests per 1,000 patients per month) in the pre- and post-MI periods were 51.9 (95% CI: 51.7, 52.1) and 84.4 (95% CI: 84.1, 84.6), respectively. Across the 12 months post-MI, observed rates were higher than model-predicted rates, with the magnitude of rate differences changing over time (Figure). The observed testing rate peaked two months post-MI (rate difference: 65.7, 95% CI: 64.6, 66.7).

Conclusions

Our findings indicate that LDL-C testing rates increased following a MI hospitalization and stayed elevated throughout the following year. Despite this increase, overall rates remained low, with only one in two patients receiving an LDL-C test in the year after MI. These results highlight a potential gap in care, particularly given the importance of LDL-C monitoring for this population to reduce risk of future ASCVD events.

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): This study was funded by Amgen, Inc. Several authors are employees and own stock in Amgen.

Community SARS-CoV-2 Surge and Within-School Transmission

OBJECTIVES

When the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic began, experts raised concerns about in-person instruction in the setting of high levels of community transmission. We describe secondary transmission of SARS-CoV-2 within North Carolina kindergarten through 12th-grade school districts during a winter surge to determine if mitigation strategies can hinder within-school transmission.

METHODS

From October 26, 2020, to February 28, 2021, 13 North Carolina school districts participating in The ABC Science Collaborative were open for in-person instruction, adhered to basic mitigation strategies, and tracked community- and school-acquired SARS-CoV-2 cases. Public health officials adjudicated each case. We combined these data with that from August 2020 to evaluate the effect of the SARS-CoV-2 winter surge on infection rates as well as weekly community- and school-acquired cases. We evaluated the number of secondary cases generated by each primary case as well as the role of athletic activities in school-acquired cases.

RESULTS

More than 100 000 students and staff from 13 school districts attended school in person; of these, 4969 community-acquired SARS-CoV-2 infections were documented by molecular testing. Through contact tracing, North Carolina local health department staff identified an additional 209 infections among >26 000 school close contacts (secondary attack rate <1%). Most within-school transmissions in high schools (75%) were linked to school-sponsored sports. School-acquired cases slightly increased during the surge; however, within-school transmission rates remained constant, from presurge to surge, with ∼1 school-acquired case for every 20 primary cases.

CONCLUSIONS

With adherence to basic mitigation strategies, within-school transmission of SARS-CoV-2 can be interrupted, even during a surge of community infections.

Lessons Learned Using Real-World Data to Emulate Randomized Trials: A Case Study of Treatment Effectiveness for Newly Diagnosed Immune Thrombocytopenia

Regulatory agencies are increasingly considering real-world evidence (RWE) to support label expansions of approved medicines. We conducted a comparative effectiveness study to emulate a proposed randomized trial of romiplostim vs. standard-of-care (SOC) therapy among patients with recently diagnosed (≤12 months) immune thrombocytopenia (ITP), that could support expansion of the romiplostim label. We discuss challenges that we encountered and solutions that were developed to address those challenges. Study size was a primary concern, particularly for romiplostim initiators, given the rarity of ITP and the stringent trial eligibility criteria. For this reason, we leveraged multiple data sources (Nordic Country Patient Registry for Romiplostim; chart review study of romiplostim initiators in Europe; Flatiron Health EMR linked with MarketScan claims). Additionally, unlike the strictly controlled clinical trial setting, platelet counts were not measured at regular intervals in the observational data sources, and therefore the end point of durable platelet response often used in trials could not be reliably measured. Instead, the median platelet count was chosen as the primary end point. Ultimately, while we observed a slightly higher median platelet count in the romiplostim group vs. SOC, precision was limited because of small study size (median difference was 11 × 10⁹ /L (95% CI: -59, 81)). We underscore the importance of conducting comprehensive feasibility assessments to identify fit-for-purpose data sources with sufficient sample size, data elements, and follow-up. Beyond technical challenges, we also discuss approaches to increase the credibility of RWE, including systematic incorporation of clinical expertise into study design decisions, and separation between decision makers and the data.

Estimating the Effectiveness of Rotavirus Vaccine Schedules

BACKGROUND

Important questions exist regarding the comparative effectiveness of alternative childhood vaccine schedules; however, optimal approaches to studying this complex issue are unclear.

METHODS

We applied methods for studying dynamic treatment regimens to estimate the comparative effectiveness of different rotavirus vaccine (RV) schedules for preventing acute gastroenteritis-related emergency department (ED) visits or hospitalization. We studied the effectiveness of six separate protocols: one- and two-dose monovalent rotavirus vaccine (RV1); one-, two-, and three-dose pentavalent rotavirus vaccine (RV5); and no RV vaccine. We used data on all infants to estimate the counterfactual cumulative risk for each protocol. Infants were censored when vaccine receipt deviated from the protocol. Inverse probability of censoring-weighted estimation addressed potentially informative censoring by protocol deviations. A nonparametric group-based bootstrap procedure provided statistical inference.

RESULTS

The method yielded similar 2-year effectiveness estimates for the full-series protocols; weighted risk difference estimates comparing unvaccinated children to those adherent to either full-series (two-dose RV1, three-dose RV5) corresponded to four fewer hospitalizations and 12 fewer ED visits over the 2-year period per 1,000 children. We observed dose-response relationships, such that additional doses further reduced risk of acute gastroenteritis. Under a theoretical intervention to fully vaccinate all children, the 2-year risk differences comparing full to observed adherence were 0.04% (95% CI = 0.03%, 0.05%) for hospitalizations and 0.17% (95% CI = 0.14%, 0.19%) for ED visits.

CONCLUSIONS

The proposed approach can generate important evidence about the consequences of delaying or skipping vaccine doses, and the impact of interventions to improve vaccine schedule adherence.

Effectiveness and Safety of Romiplostim Among Patients with Newly Diagnosed, Persistent and Chronic Immune Thrombocytopenia in European Clinical Practice

INTRODUCTION

Romiplostim has been approved in Europe since 2009 to treat patients with chronic primary immune thrombocytopenia (ITP). Using real-world data from seven European countries, we measured the effectiveness and safety outcomes within 24 weeks following romiplostim initiation by duration of ITP: less than 3 months ("newly diagnosed"), 3-12 months ("persistent"), and more than 12 months ("chronic").

METHODS

Adults with ITP and ≥ 1 romiplostim administration between 2009 and 2012 were included. Endpoints included durable platelet response, median platelet count, rescue therapy, bleeding and adverse events. We used inverse probability of censoring weighted estimators to estimate cumulative risk of each outcome. There were 64 newly diagnosed, 50 persistent, and 226 chronic ITP patients at romiplostim initiation.

RESULTS

Durable platelet response at 24 weeks ranged from 32% [confidence interval (CI): 18-46%] in newly diagnosed patients to 53% (CI 37-68%) in persistent patients. Median platelet count during follow-up ranged from 88 (CI 80-96) × 10⁹/L in chronic patients to 131 (CI 102-160) × 10⁹/L in newly diagnosed patients.

CONCLUSION

Regardless of ITP duration, over half of patients discontinued concomitant ITP medications. Few adverse events were observed. Although only approved for chronic patients, estimates of the romiplostim treatment effect were similar across patients being managed in European clinical practice, regardless of ITP duration at romiplostim initiation.

Incidence and Secondary Transmission of SARS-CoV-2 Infections in Schools

BACKGROUND

In an effort to mitigate the spread of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), North Carolina closed prekindergarten through grade 12 public schools to in-person instruction on March 14, 2020. On July 15, 2020, North Carolina's governor announced schools could open via remote learning or a hybrid model that combined in-person and remote instruction. In August 2020, 56 of 115 North Carolina school districts joined The ABC Science Collaborative (ABCs) to implement public health measures to prevent SARS-CoV-2 transmission and share lessons learned. We describe secondary transmission of SARS-CoV-2 within participating school districts during the first 9 weeks of in-person instruction in the 2020-2021 academic year.

METHODS

From August 15, 2020 to October 23, 2020, 11 of 56 school districts participating in ABCs were open for in-person instruction for all 9 weeks of the first quarter and agreed to track incidence and secondary transmission of SARS-CoV-2. Local health department staff adjudicated secondary transmission. Superintendents met weekly with ABCs faculty to share lessons learned and develop prevention methods.

RESULTS

Over 9 weeks, 11 participating school districts had >90 000 students and staff attend school in person. Among these students and staff, 773 community-acquired SARS-CoV-2 infections were documented by molecular testing. Through contact tracing, health department staff determined an additional 32 infections were acquired within schools. No instances of child-to-adult transmission of SARS-CoV-2 were reported within schools.

CONCLUSIONS

In the first 9 weeks of in-person instruction in North Carolina schools, we found extremely limited within-school secondary transmission of SARS-CoV-2, as determined by contact tracing.

Informing Healthcare Decisions with Observational Research Assessing Causal Effect. An Official American Thoracic Society Research Statement

Rationale: Decisions in medicine are made on the basis of knowledge and reasoning, often in shared conversations with patients and families in consideration of clinical practice guideline recommendations, individual preferences, and individual goals. Observational studies can provide valuable knowledge to inform guidelines, decisions, and policy.

Objectives: The American Thoracic Society (ATS) created a multidisciplinary ad hoc committee to develop a research statement to clarify the role of observational studies—alongside randomized controlled trials (RCTs)—in informing clinical decisions in pulmonary, critical care, and sleep medicine.

Methods: The committee examined the strengths of observational studies assessing causal effects, how they complement RCTs, factors that impact observational study quality, perceptions of observational research, and, finally, the practicalities of incorporating observational research into ATS clinical practice guidelines.

Measurements and Main Results: There are strengths and weakness of observational studies as well as RCTs. Observational studies can provide evidence in representative and diverse patient populations. Quality observational studies should be sought in the development of ATS clinical practice guidelines, and medical decision-making in general, when 1) no RCTs are identified or RCTs are appraised as being of low- or very low-quality (replacement); 2) RCTs are of moderate quality because of indirectness, imprecision, or inconsistency, and observational studies mitigate the reason that RCT evidence was downgraded (complementary); or 3) RCTs do not provide evidence for outcomes that a guideline committee considers essential for decision-making (e.g., rare or long-term outcomes; “sequential”).

Conclusions: Observational studies should be considered in developing clinical practice guidelines and in making clinical decisions.

G-estimation of structural nested mean models for competing risks data using pseudo-observations

This article provides methods of causal inference for competing risks data. The methods are formulated as structural nested mean models of causal effects directly related to the cumulative incidence function or subdistribution hazard, which reflect the survival experience of a subject in the presence of competing risks. The effect measures include causal risk differences, causal risk ratios, causal subdistribution hazard ratios, and causal effects of time-varying exposures. Inference is implemented by g-estimation using pseudo-observations, a technique to handle censoring. The finite-sample performance of the proposed estimators in simulated datasets and application to time-varying exposures in a cohort study of type 2 diabetes are also presented.