Implementation outcomes included in NIDA Clinical Trials Network (CTN) studies: A systematic review of studies conducted over 20 years.

BACKGROUND: The National Institute on Drug Abuse (NIDA) Clinical Trials Network (CTN) has supported clinical trials of substance use disorder (SUD) interventions for 25 years. This review describes the use of implementation outcomes across CTN trials, characterizes outcomes included, and identifies gaps and potential opportunities to strengthen implementation research within the CTN and the field of SUD treatment. METHODS: This systematic review included active or completed studies listed on the CTN Dissemination Library webpage as of August 18, 2021, and approved by the CTN for development by January 1, 2022. Study summaries and protocols were reviewed if they: 1) measured at least one implementation outcome and 2) examined a practice change, intervention, or process. Extracted data elements included trial design characteristics, implementation frameworks, and outcome assessment domains informed by the RE-AIM and Proctor Implementation Outcomes Frameworks. RESULTS: 114 protocols were considered, 42 full-text protocols were screened, and 25 were included for data extraction. Start dates of trials spanned a 20-year period (2004-2024) with latter studies including more implementation outcomes. Fidelity (n = 29) and reach/penetration (n = 26) were the most included implementation outcomes. Equity was not identified in any protocols. Methods of defining, capturing, and evaluating outcomes data varied across trials and outcomes. CONCLUSION: The inclusion of implementation outcomes increased over time, perhaps reflecting a growing emphasis on implementation research. Incorporating measures of equity could advance knowledge about differential receipt or effectiveness of SUD interventions. Future research should seek to improve the consistency and comprehensiveness in descriptions of implementation science elements.