Mediation-aligned analysis with a survival outcome and missing data using med4way: Decomposing the effect of contingency management on appointment attendance through therapeutic alliance

Contingency management (CM)—a behavioral intervention using positive reinforcement such as financial incentives—has strong evidence supporting its use in opioid use disorder (OUD) treatment. Individuals being treated for OUD receive opiate agonist treatment and regular keywork appointments at the start of treatment, with continuous attendance representing a positive outcome. Therapeutic alliance (TA) between patient and keyworker is a proposed process variable through which some of the effect of CM may operate. This presentation examines the extent to which CM's effect on treatment attendance is transmitted via TA, relative to treatment as usual (TAU). This presented two analytic challenges: modeling the time-to-nonattendance outcome as a survival outcome and addressing the substantial amount of missing TA data. We present a principled approach to both challenges within a mediation framework, implemented using the med4way command with the bootstrap function, and multiple imputation procedures in Stata.