Community-based clinical trials: Site variation and adoption of innovation.

The National Drug Abuse Treatment Clinical Trials Network (CTN) conducts multi-site clinical trials in community-based drug abuse treatment centers to test the effectiveness and generalizability of emerging pharmacological and behavioral therapies for drug addiction. Site differences are common in multi-site trials but the sources of the variation are unclear. A trial of interventions to reduce HIV risk behaviors, for example, found that a site characteristic (distance between a detoxification center and an outpatient center) was the strongest predictor of entering outpatient care following detoxification. To begin to address site variation, the CTN collects workforce and organizational data at participating sites prior to implementing new trials. Data from four trials suggest that sites varied prior to trial implementation on staff composition (e.g., % counselors with graduate degrees, % counselors in recovery), and clinical director commitment to implementation. Sites also vary on how the protocol is organized and implemented within each treatment center. Clinical directors were more committed to protocol implementation than counselors. Counselors were more committed to implementation of a twelve-step facilitation protocol than to a smoking cessation protocol. Variation was apparent both within and across trials. The variation may affect protocol implementation and influence client outcomes. Future analyses will link site data with patient outcomes. It is essential to begin to understand the sources of site variation in outcomes.