Abstract
The HIV risk-taking behavior scale (HRBS) is an 11-item instrument designed to assess the risks of HIV infection due to self-reported injection-drug use and sexual behavior. A retrospective analysis was performed on HRBS data collected from approximately 1,000 participants pooled across seven clinical trials of pharmacotherapies for either the treatment of cocaine dependence or methamphetamine dependence. Analysis faced three important challenges. The sample contained a high proportion of missing assessments after randomization. Also, the HRBS scale consists of two distinct behavioral components which may or may not coincide in response patterns. In addition, distributions of responses on the subscales were highly concentrated at just a few values (e.g., 0, 6). To address these challenges, a single probit regression model was fit to three outcomes variables simultaneously – the two subscale totals plus an indicator variable for assessments not obtained (non-response). This joint-outcome regression model was able to identify that those who left assessment early had higher self-reported risk of injection-drug use and lower self-reported risky sexual behavior because the model was able to draw on information on associations among the three outcomes collectively. These findings were not identified in analyses performed on each outcome separately. No evidence for an effect of pharmacotherapies was observed, except to reduce missing assessments. Univariate-outcome modeling is not recommended for the HRBS.
Highlights
Injection-drug users are susceptible to HIV infection through injection, especially given HIV’s extended viability within syringes (Abdala et al, 1999), and through unprotected sexual contact with those infected with HIV, including other injectiondrug users (Strathdee and Stockman, 2010)
The purpose of this paper is to address the analytic challenges of the HIV risk-taking behavior scale (HRBS) simultaneously in a single, comprehensive regression modeling framework and thereby provide investigators with a toolkit for evaluating longitudinal HRBS assessments
Self-reported risky sexual behaviors may have been more amenable to counseling and thereby declined because these behaviors were adjunct to the primary disorder within the recruitment population
Summary
Injection-drug users are susceptible to HIV infection through injection, especially given HIV’s extended viability within syringes (Abdala et al, 1999), and through unprotected sexual contact with those infected with HIV, including other injectiondrug users (Strathdee and Stockman, 2010). A recent estimate of the quantity of HIV infected injection-drug users worldwide is 0.8–6.6 million (Mathers et al, 2008). The HIV risk-taking behavior scale (HRBS) is an 11-item instrument designed to assess “the behavior of intravenous drug users in relation to both injecting and sexual behavior” (Darke et al, 1991). Six items assess injection-drug use and five items assess sexual behavior. Darke et al (1991) reported an estimated internal reliability of α ≈ 0.70, test–retest reliability of r ≈ 0.86, and item-level percentage agreement with surrogates exceeding 81%. Six items assess injection-drug use and five items assess sexual behavior. Darke et al (1991) reported an estimated internal reliability of α ≈ 0.70, test–retest reliability of r ≈ 0.86, and item-level percentage agreement with surrogates exceeding 81%. Petry (2001) reported similar estimates of reliability in a separate study
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