### Department of Biostatistics Seminar/Workshop Series

# **Regression modeling of longitudinal binary outcomes with outcome-dependent observation times**** **

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**## Benjamin French, PhD

##### Assistant Professor, Department of Biostatistics and Epidemiology, Perelman School of Medicine, University of Pennsylvania

**Regression modeling of longitudinal binary outcomes with outcome-dependent observation times**
Conventional longitudinal data analysis methods assume that outcomes are independent of the data-collection schedule. However, the independence assumption may be violated, for example, when adverse events trigger additional physician visits in between prescheduled follow-ups. Observation times may therefore be associated with outcome values, which may introduce bias when estimating the effect of covariates on outcomes using standard longitudinal regression methods. Existing semi-parametric methods that accommodate outcome-dependent observation times are limited to the analysis of continuous outcomes. We develop new methods for the analysis of binary outcomes, while retaining the flexibility of semi-parametric models. Our methods are based on counting process approaches, rather than relying on possibly intractable likelihood-based or pseudo-likelihood-based approaches, and provide marginal, population-level inference. We illustrate the utility of our proposed methods using data from a randomized controlled trial of interventions designed to improve adherence to warfarin therapy. We show that our methods perform well in the presence of outcome-dependent observation times, and provide identical inference to ‘naive’ approaches when observation times are not associated with outcomes.
-- AudreyCarvajal - 05 Nov 2013 **
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