Generalizability of the findings from a randomized controlled trial of a web-based substance use disorder intervention.

Abstract

There is growing concern regarding the generalizability of findings from randomized controlled trials (RCTs) of interventions for substance use disorders (SUDs). This study used a selection model approach to assess and improve the generalizability of an evaluation for a web-based SUD intervention by making the trial sample resemble the target population. The sample of the web-based SUD intervention (Therapeutic Education System vs. Treatment-as-usual; n = 507) was compared with the target population of SUD treatment-seeking individuals from the Treatment Episodes Data Set-Admissions (TEDS-A). Using weights based on the probabilities of RCT participation, we computed weighted treatment effects on retention and abstinence. Substantial differences between the RCT sample and the target population was demonstrated in significant difference in the mean propensity scores (1.62 standard deviations at p < .001). The population effect on abstinence (12 weeks and 6 months) was statistically insignificant after weighting the data with the generalizability weight. Generalizability of the findings from the RCT could be limited when the RCT sample does not well represent the target population. Application of generalizability weights can be a potentially useful tool to improve generalizability of RCT findings. (Am J Addict 2018;27:231-237).