Treatment Heterogeneity and Individual Qualitative Interaction

• Activity Number: 232
• Type: Contributed
• Date/Time: Monday, August 1, 2011 : 2:00 PM to 3:50 PM
• Sponsor: Biometrics Section
• Author(s): Gary L. Gadbury*+ and Robert S. Poulson and David B. Allison
• Companies: Kansas State University and University of Alabama at Birmingham
• Keywords: Causation ; Crossover interaction ; Individual effects ; Potential outcomes ; Subject-treatment interaction

Abstract

Plausibility of high variation in treatment effects across individuals has been recognized as an important consideration in clinical studies. Surprisingly, little attention has been given to evaluating this variability in design of clinical trials or analyses of resulting data. High variation across individuals (referred to herein as treatment heterogeneity) in a treatments efficacy and/or safety across individuals may have important consequences because the optimal treatment choice for an individual may be different from that suggested by a study of average effects. We call this an individual qualitative interaction (IQI), borrowing terminology from earlier work - referring to a qualitative interaction (QI) being present when the optimal treatment varies across "groups" of individuals. We use a potential outcomes framework to elucidate connections between IQI and the probability of a similar response (PSR). We do so under a potential outcomes framework that can add insights to results from usual data analyses and to study design features that improve the capability to more directly assess treatment heterogeneity.