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Data Mining for Adverse Drug Events With a Propensity Score-matched Tree-based Scan Statistic

Wang, Shirley V.a; Maro, Judith C.b; Baro, Elandec; Izem, Rimac; Dashevsky, Innab; Rogers, James R.a; Nguyen, Michaeld; Gagne, Joshua J.a; Patorno, Elisabettaa; Huybrechts, Krista F.a; Major, Jacqueline M.d; Zhou, Estherd; Reidy, Meganb; Cosgrove, Austinb; Schneeweiss, Sebastiana; Kulldorff, Martina

doi: 10.1097/EDE.0000000000000907

The tree-based scan statistic is a statistical data mining tool that has been used for signal detection with a self-controlled design in vaccine safety studies. This disproportionality statistic adjusts for multiple testing in evaluation of thousands of potential adverse events. However, many drug safety questions are not well suited for self-controlled analysis. We propose a method that combines tree-based scan statistics with propensity score–matched analysis of new initiator cohorts, a robust design for investigations of drug safety. We conducted plasmode simulations to evaluate performance. In multiple realistic scenarios, tree-based scan statistics in cohorts that were propensity score matched to adjust for confounding outperformed tree-based scan statistics in unmatched cohorts. In scenarios where confounding moved point estimates away from the null, adjusted analyses recovered the prespecified type 1 error while unadjusted analyses inflated type 1 error. In scenarios where confounding moved point estimates toward the null, adjusted analyses preserved power, whereas unadjusted analyses greatly reduced power. Although complete adjustment of true confounders had the best performance, matching on a moderately mis-specified propensity score substantially improved type 1 error and power compared with no adjustment. When there was true elevation in risk of an adverse event, there were often co-occurring signals for clinically related concepts. TreeScan with propensity score matching shows promise as a method for screening and prioritization of potential adverse events. It should be followed by clinical review and safety studies specifically designed to quantify the magnitude of effect, with confounding control targeted to the outcome of interest.

From the aDivision of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Harvard Medical School and Brigham and Women’s Hospital, Boston, MA

bDepartment of Population Medicine, Harvard Medical School and Harvard Pilgrim Health Care Institute, Boston, MA

cOffice of Biostatistics, Center for Drug Evaluation and Research, U.S. Food and Drug Administration

dOffice of Surveillance and Epidemiology, Center for Drug Evaluation and Research, U.S. Food and Drug Administration, Silver Spring, MD.

Submitted December 19, 2017; accepted July 27, 2018.

The data underlying the simulation was licensed from Optum Clinformatics.

The Sentinel task order was funded by the FDA through the Department of Health and Human Services (HHS) Contract number HHSF22301010T-0004.

Disclaimer: This article reflects the views of the authors and should not be construed to represent FDA’s views or policies.

At the time that this work was conducted, Dr. Wang was principal investigator on other grants from: Agency for Healthcare Research Quality (AHRQ), Food and Drug Administration (FDA) Sentinel Program, and an investigator initiated grant from Novartis for unrelated research. Dr. Wang is a consultant to Aetion, Inc., a software company. Dr. Gagne has received salary support from grants from Novartis Pharmaceuticals Corporation and Eli Lilly and company to Brigham and Women’s Hospital and is a consultant to Aetion, Inc. and to Optum, Inc., all for unrelated work. James Rogers is a consultant to Aetion, Inc. Dr. Schneeweiss is consultant to WHISCON, LLC and to Aetion, Inc., a software manufacturer of which he also owns equity. He is a principal investigator of investigator-initiated grants to the Brigham and Women’s Hospital from Bayer, Genentech and Boehringer Ingelheim for unrelated research.

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Correspondence: Shirley V. Wang, Division of Pharmacoepidemiology and Pharmacoeconomics, Department of Medicine, Harvard Medical School and Brigham and Women’s Hospital, 1620 Tremont St, Suite 3030, Boston, MA 02120. E-mail:

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