Correlates of Validity of Self-Reported Methamphetamine Use among a Sample of Dependent Adults.

BACKGROUND: Self-reported data are widely used in substance-use research, yet few studies have assessed the validity of self-reported methamphetamine use compared to biological assays.

OBJECTIVES: We sought to assess the validity and correlates of validity of self-reported methamphetamine use compared to urine toxicology (UTOX).

METHODS: Using a sample of methamphetamine-dependent individuals enrolled in a randomized controlled pharmacotherapy trial in the United States (n = 327 visits among 90 participants), we calculated sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and the kappa coefficient of self-reported methamphetamine use in the past 3 days compared to UTOX, as well as the NPV of self-reported methamphetamine use over an extended recall period of 1 month. We used multivariable logistic regression models to assess correlates of concordance between self-reported methamphetamine use and UTOX.

RESULTS: The sensitivity of self-reported methamphetamine use in the past 3 days was 86.7% (95% confidence intervals (95%CI): 81.4%-91.4%), the specificity was 85.3% (77.7-91.3), the PPV was 91.5% (86.9-94.8), and the NPV was 78.0% (69.4-86.1), compared to UTOX (kappa = 0.71). The NPV over the extended recall period was 70.6% (48.0-85.7). In multivariable analyses, validity of self-reported methamphetamine use was higher for older participants but lower during follow-up compared to baseline and when polysubstance use or depressive symptoms were reported. Conclusions/Importance: Our sample of methamphetamine-dependent adults reported recent methamphetamine use with high validity compared to UTOX. Validity increased with age but decreased when participants reported depressive symptoms or polysubstance use as well as later in the study timeline and during longer recall periods.