Shirley V. Wang

Estimation using all available covariate information versus a fixed look-back window for dichotomous covariates

When using claims data, dichotomous covariates (C) are often assumed to be absent unless a claim for the condition is observed. When available historical data differs among subjects, investigators must choose between using all available historical data versus data from a fixed window to assess C. Our purpose was to compare estimation under these two approaches.

A modular, prospective, semi-automated drug safety-monitoring system for use in a distributed data environment

The aim of this study was to develop and test a semi‐automated process for conducting routine active safety monitoring for new drugs in a network of electronic healthcare databases.

Prediction of rates of thromboembolic and major bleeding outcomes with dabigatran or warfarin among patients with atrial fibrillation: new initiator cohort study

Objectives To compare stratified event rates from randomized controlled trials with predicted event rates from models developed in observational data, and assess their ability to accurately capture observed rates of thromboembolism and major bleeding for patients treated with dabigatran or warfarin as part of routine care. Design New initiator cohort study. Setting Data from United Health (October 2009 to June 2013), a commercial healthcare claims database in the United States. Participants 21 934 adults with atrial fibrillation initiating dabigatran (150 mg dose only) or warfarin treatment as part of routine care. Main outcome measures Predicted annual rates of thromboembolism or major bleeding, based on estimates from randomized controlled trials, models developed in routine care patients, and baseline risk scores (CHADS2, CHA2DS2-VASc, and HAS-BLED). Thromboembolism was a composite outcome, including primary inpatient diagnosis codes for ischemic or ill defined stroke, transient ischemic attack, pulmonary embolism, deep vein thrombosis, and systemic embolism. Major bleeding was a composite outcome including codes occurring in an inpatient setting for hemorrhagic stroke; major upper, lower, or unspecified gastrointestinal bleed; and major urogenital or other bleed. Results 6516 (30%) and 15 418 (70%) of patients initiated dabigatran and warfarin, respectively. Annual event rates per 100 patients were 1.7 for thromboembolism and 4.6 for major bleeding. For thromboembolism, calibration of estimates from randomized controlled trials was similar to calibration for model based predictions; however, trial estimates for major bleeding consistently underestimated the rate of bleeding among patients in routine care. Underestimation of bleeding rates was particularly pronounced in warfarin initiators with high HAS-BLED scores, where event rates were underestimated by up to 4.0 per 100 patient years. Harrell’s c indices for discrimination for thromboembolism or major bleeding in dabigatran and warfarin initiators ranged between 0.59 and 0.66 for randomized controlled trial predictions, and between 0.52 and 0.70 for cross validated model based predictions. Conclusion Estimated rates of thromboembolism under dabigatran or warfarin treatment in randomized controlled trials were close to observed rates in routine care patients. However, rates of major bleeding were underestimated. Models developed in routine care patients can provide accurate, tailored estimates of risk and benefit under alternative treatment to enhance patient centered care.

Age, Antipsychotics, and the Risk of Ischemic Stroke in the Veterans Health Administration

Background and Purpose— Time-dependent effects of antipsychotics on risk of stroke and potential effect modification by age have not been fully investigated. A case–case–time–control design uses within- and between-case comparisons to evaluate short-term effects at the same time as adjusting for unmeasured time-invariant confounders and exposure-time trends. Methods— We conducted a case–case–time–control design study using data from the Veterans Health Administration. Veterans with inpatient hospitalizations for ischemic stroke between 2002 and 2007 were included. For every stroke case, the “current” exposure period was defined as 1 to 30 days before hospitalization and the “reference” period as 91 to 120 days before hospitalization. Exposure during the current period was compared with exposure during the reference period within cases. Exposure-time trend-adjusted estimates of the effect of antipsychotic exposure on risk of stroke were obtained by dividing exposure odds for antipsychotic exposure by average exposure odds for other medications over the same time period among the same cases. Results— After adjusting for exposure-time trends, odds of stroke were 1.8 (95% CI, (1.7–1.9) times higher when exposed to antipsychotics than when unexposed. Age-stratified estimates suggest a greater triggering effect of antipsychotics among older patients. Conclusions— Exposure to antipsychotics may be a proximal trigger for stroke. Elevation in risk is apparent after brief exposure to antipsychotics.

Switching generic antiepileptic drug manufacturer not linked to seizures: A case-crossover study

Objective: With more antiepileptic drugs (AED) becoming available in generic form, we estimated the risk of seizure-related events associated with refilling generic AEDs and the effect of switching between different manufacturers of the same generic drug. Methods: We designed a population-based case-crossover study using the Medicaid Analytic eXtract and a US commercial health insurance database. We identified 83,001 generic AED users who experienced a seizure-related hospital admission or emergency room visit between 2000 and 2013 and assessed whether they received a refill of the same AED from the same manufacturer or a different manufacturer. Patients served as their own controls and conditional logistic regression was used to compare exposure to a refill during the hazard period, defined as days 2–36 preceding the seizure-related event, to exposure during the control period, defined as days 51–85 preceding the seizure-related event. Results: Generic AED refilling was associated with an 8% increase in the odds of seizure-related events (odds ratio [OR] 1.08; 95% confidence interval [CI] 1.06–1.11). The OR following a switch to a different manufacturer of the same AED was 1.09 (95% CI 1.03–1.15); however, after adjusting for the process of refilling, there was no association between switching and seizure-related hospital visits (OR 1.00; 95% CI 0.94–1.07). Conclusions: Among patients on a generic AED, refilling the same AED was associated with an elevated risk of seizure-related event; however, there was no additional risk from switching during that refill to a different manufacturer. Generic AEDs available to US patients, with Food and Drug Administration–validated bioequivalence, appear to be safe clinical choices.

Successful Comparison of US Food and Drug Administration Sentinel Analysis Tools to Traditional Approaches in Quantifying a Known Drug‐Adverse Event Association

The US Food and Drug Administrations Sentinel system has developed the capability to conduct active safety surveillance of marketed medical products in a large network of electronic healthcare databases. We assessed the extent to which the newly developed, semiautomated Sentinel Propensity Score Matching (PSM) tool could produce the same results as a customized protocol‐driven assessment, which found an adjusted hazard ratio (HR) of 3.04 (95% confidence interval [CI], 2.81–3.27) comparing angioedema in patients initiating angiotensin‐converting enzyme (ACE) inhibitors vs. beta‐blockers. Using data from 13 Data Partners between 1 January 2008, and 30 September 2013, the PSM tool identified 2,211,215 eligible ACE inhibitor and 1,673,682 eligible beta‐blocker initiators. The tool produced an HR of 3.14 (95% CI, 2.86–3.44). This comparison provides initial evidence that Sentinel analytic tools can produce findings similar to those produced by a highly customized protocol‐driven assessment.

Transparency and Reproducibility of Observational Cohort Studies Using Large Healthcare Databases.

The scientific community and decision‐makers are increasingly concerned about transparency and reproducibility of epidemiologic studies using longitudinal healthcare databases. We explored the extent to which published pharmacoepidemiologic studies using commercially available databases could be reproduced by other investigators. We identified a nonsystematic sample of 38 descriptive or comparative safety/effectiveness cohort studies. Seven studies were excluded from reproduction, five because of violation of fundamental design principles, and two because of grossly inadequate reporting. In the remaining studies, >1,000 patient characteristics and measures of association were reproduced with a high degree of accuracy (median differences between original and reproduction <2% and <0.1). An essential component of transparent and reproducible research with healthcare databases is more complete reporting of study implementation. Once reproducibility is achieved, the conversation can be elevated to assess whether suboptimal design choices led to avoidable bias and whether findings are replicable in other data sources.

Reporting to Improve Reproducibility and Facilitate Validity Assessment for Healthcare Database Studies V1.0

Defining a study population and creating an analytic dataset from longitudinal healthcare databases involves many decisions. Our objective was to catalogue scientific decisions underpinning study execution that should be reported to facilitate replication and enable assessment of validity of studies conducted in large healthcare databases.

Sentinel Modular Program for Propensity Score–Matched Cohort Analyses: Application to Glyburide, Glipizide, and Serious Hypoglycemia

Sentinel is a program sponsored by the US Food and Drug Administration to monitor the safety of medical products. We conducted a cohort assessment to evaluate the ability of the Sentinel Propensity Score Matching Tool to reproduce in an expedited fashion the known association between glyburide (vs. glipizide) and serious hypoglycemia. Thirteen data partners who contribute to the Sentinel Distributed Database participated in this analysis. A pretested and customizable analytic program was run at each individual site. De-identified summary results from each data partner were returned and aggregated at the Sentinel Operations Center. We identified a total of 198,550 and 379,507 new users of glyburide and glipizide, respectively. The incidence of emergency department visits and hospital admissions for serious hypoglycemia was 19 per 1000 person-years (95% confidence interval = 17.9, 19.7) for glyburide users and 22 (21.6, 22.7) for glipizide users. In cohorts matched by propensity score based on predefined variables, the hazard ratio (HR) for glyburide was 1.36 (1.24, 1.49) versus glipizide. In cohorts matched on a high-dimensional propensity score based on empirically selected variables, for which the program ran to completion in five data partners, the HR was 1.49 (1.31, 1.70). In cohorts matched on propensity scores based on both predefined and empirically selected variables via the high-dimensional propensity score algorithm (the same five data partners), the HR was 1.51 (1.32, 1.71). These findings are consistent with the literature, and demonstrate the ability of the Sentinel Propensity Score Matching Tool to reproduce this known association in an expedited fashion. See video abstract at, http://links.lww.com/EDE/B275.

Pharmacoepidemiological assessment of drug interactions with vitamin K antagonists

We present a database of prescription drugs and international normalized ratio (INR) data and the applied methodology for its use to assess drug–drug interactions with vitamin K antagonists (VKAs). We use the putative interaction between VKAs and tramadol as a case study.