Enrollment factors and bias of disease prevalence estimates in administrative claims data Elizabeth T. Jensen, MPH PhD 1,2 , Suzanne F. Cook, PhD 3 , Jeffery K. Allen, MS 3 , John Logie, PhD 3 , M. Alan Brookhart, PhD 4 , Michael D. Kappelman, MD MPH 2,5 , and Evan S. Dellon, MD MPH 1,2 1 Center for Esophageal Diseases and Swallowing, Division of Gastroenterology and Hepatology, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, NC 2 Center for Gastrointestinal Biology and Disease, Division of Gastroenterology and Hepatology, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, NC 3 GlaxoSmithKline, Gillings Global School of Public Health, University of North Carolina, Chapel Hill, NC 4 Department of Epidemiology, Gillings Global School of Public Health, University of North Carolina, Chapel Hill, NC 5 Division of Pediatric Gastroenterology and Hepatology, Department of Pediatrics, University of North Carolina School of Medicine, Chapel Hill, NC Abstract Purpose—Considerations for using administrative claims data in research have not been well- described. To increase awareness of how enrollment factors and insurance benefit use may contribute to observed estimates, we evaluated how differences in operational definitions of the cohort impacted estimates of disease prevalence. Methods—We conducted a cross-sectional study estimating the prevalence of five gastrointestinal conditions using MarketScan claims data for 73.1 million enrollees. We extracted data obtained from 2009–2012 to identify cohorts meeting various enrollment, prescription drug benefit, or healthcare utilization characteristics. Next, we identified patients meeting the case definition for each of the diseases of interest. We compared the estimates obtained to evaluate the influence of enrollment period, drug benefit, and insurance usage. Corresponding Author: Elizabeth Jensen, MPH PhD, CB #7080 – 4140 Bioinformatics Building, 130 Mason Farm Rd., UNC-CH, Chapel Hill, NC 27599-7080, Phone: 1-919-428-5091, Fax: 1-919-843-2508, elizabeth_jensen@med.unc.edu. Potential competing interests: None Specific author contributions (all authors approved the final draft): Jensen: Project conception, study design, data interpretation, manuscript drafting, critical revision Cook: Study design, data interpretation, critical revision Allen: Study design, data analyses, data interpretation, critical revision Logie: Study design, data analyses, data interpretation, critical revision Brookhart: Project conception, study design, data interpretation, critical revision Kappelman: Study design, data interpretation, critical revision Dellon: Project conception, study design, data interpretation, manuscript drafting, critical revision HHS Public Access Author manuscript Ann Epidemiol. Author manuscript; available in PMC 2016 July 01. Published in final edited form as: Ann Epidemiol. 2015 July ; 25(7): 519–525.e2. doi:10.1016/j.annepidem.2015.03.008. Author Manuscript Author Manuscript Author Manuscript Author Manuscript