Exploring the mediating role of baseline urinalysis results on demographic characteristics and stimulant use disorder treatment outcomes.

Introduction: Baseline stimulant urinalysis (UA) is one of the most reliable predictors of stimulant use disorder treatment outcomes. Yet we know little about the role of baseline stimulant UA mediating the effects of different baseline characteristics on treatment outcomes.

Objectives: This study aimed to explore the potential mediating role of baseline stimulant UA results on the relationship between baseline characteristics and total number of stimulant negative UAs submitted during treatment.

Methods: The study team conducted analyses on data from a multisite randomized clinical trial of contingency management (CM) targeting stimulant use among individuals enrolled in methadone maintenance treatment programs (n = 394). Baseline characteristics included trial arm, education, race, sex, age, and Addiction Severity Index (ASI) composite measures. Baseline stimulant UA was the mediator and total number of stimulant negative UAs provided during treatment was the primary outcome variable.

Results: The baseline characteristics of sex (OR = 1.85), ASI drug (OR = 0.01) and psychiatric (OR = 6.20) composites were directly associated with the baseline stimulant UA result (p < 0.05 for all). Baseline stimulant UA result (B = -8.24), trial arm (B = -2.55), ASI drug composite (B = -8.38) and education (B = -1.95) were directly associated with the total number of negative UAs submitted (p < 0.05 for all). The evaluation of indirect effects of baseline characteristics on the primary outcome through baseline stimulant UA revealed significant mediated effects for the ASI drug composite (B = -5.50) and age (B = -0.05; p < 0.05 for both).

Conclusions: Baseline stimulant UA is a strong predictor of stimulant use treatment outcomes and mediates the association of some baseline characteristics and a stimulant use treatment outcome.