43: Zero-Inflated Outcomes in Sequential, Multiple Assignment, Randomized Trials

Thomas M. Menino Convention & Exhibition Center 

A Sequential, Multiple Assignment, Randomized Trial (SMART) is a clinical trial design for developing and comparing dynamic treatment regimens. Standard SMART analyses often use weighted and replicated regression. In non-SMART studies with count outcomes, especially in settings of substance use, zero-inflation is a common issue.

One solution for zero-inflated longitudinal outcomes is the two-part hurdle model (HM). This model handles random zero cases where subjects have zero outcomes but remain at risk. HMs have not yet been applied to SMART data.

We propose a two-part HM for zero-inflated, longitudinal count outcomes in SMARTs. The model combines logistic regression for zero/nonzero outcomes with a truncated Poisson model for nonzero counts. Our approach is motivated by and applied to the SafERteens M-Coach SMART, which studied investigated the effects of brief interventions and text messaging on young adults on alcohol consumption outcomes.

Sequential Multiple Assignment Randomized Trial

Zero-Inflated Outcomes

Clinical Trial Methods

Poisson Regression

Longitudinal Data 

Mental Health Statistics Section