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Assessing Sample Representativeness in Randomized Clinical Trials: Application to the National Institute of Drug Abuse Clinical Trials Network.

Ryoko Susukida, PhD, Rosa M. Crum, MD, Elizabeth A. Stuart, PhD, Cyrus Ebnesajjad, MA, Ramin Mojtabai, MD (all from Johns Hopkins University).

Addiction 2016;111(7):1226-1234. [doi: 10.1111/add.13327]

Randomized controlled trials (RCTs) are generally considered the gold standard for establishing the effectiveness of new interventions. However, lack of external validity, which indicates how well findings from one particular setting can apply to the target population, can be an issue with many RCTs. This study aimed to compare characteristics of individuals participating in randomized controlled trials of treatments of substance use disorder (SUD) with individuals receiving treatment in usual care settings, and to provide a summary quantitative measure of differences between characteristics of these two groups of individuals using propensity score methods.

Analyses using data from RCT samples from multiple sites in the NIDA Clinical Trials Network (CTN) and target populations of patients drawn from the Treatment Episodes Data Set-Admissions (TEDS-A) were performed. Participants included a total of 3,592 individuals from 10 CTN samples and 1,602,226 individuals selected from TEDS-A between 2001 and 2009.

Propensity scores for enrolling in the RCTs ere computed based on the following nine observable characteristics: sex, race/ethnicity, age, education, employment status, marital status, admission to treatment through criminal justice, intravenous drug use, and the number of prior treatments. The proportion of those with 12 or more years of education and the proportion of those who had full-time jobs were significantly higher among RCT samples than among target populations (in seven and nine trials, respectively). The pooled difference in the mean propensity scores between the RCTs and the target population was 1.54 standard deviations and was statistically significant at p<.001.

Conclusions: In the U.S., individuals recruited into randomized controlled trials (RCTs) of substance use disorder treatments appear to be very different from individuals receiving treatment in usual care settings. Notably, RCT participants tend to have more years of education and a greater likelihood of full-time work compared with people receiving care in usual care settings. Representativeness of the trial samples in future CTN trials should be carefully considered, particularly because the primary mission of the CTN was to improve the quality of SUD treatment nationwide. Less stringent exclusion criteria may improve generalizability and result in more representative samples in SUD treatment RCTs. (Article, Peer-Reviewed, PDF, English, 2016)

Keywords: Clinical trials - Methods | CTN platform/ancillary study | National Drug Abuse Treatment Clinical Trials Network | Research design | Research participation | Addiction (journal)

Document No: 1185, PMID: 26825855, PMCID: PMC4899104.

Submitted by CTN Dissemination Librarians, 2/8/2016.

Crum, Rosa M.
Ebnesajjad, Cyrus
Stuart, Elizabeth A.
Susukida, Ryoko mail
Mojtabai, Ramin

Supported by a grant from the National Institute on Drug Abuse to the University of Washington Alcohol and Drug Abuse Institute.
The materials on this site have neither been created nor reviewed by NIDA.
Updated 7/2017 --