Background: Self-reports of medication adherence are subject to recall errors and social desirability bias. The visual analogue scale (VAS) is a brief measure and minimally burdensome. Its accuracy among substance users needs confirmation. Methods: We administered the VAS on an audio computer-assisted self-interview (ACASI) to 102 HIV-positive active substance users. Viral load (VL) was obtained via chart review. Cohen κ assessed the overall agreement between VL suppression and adherence, and a receiver–operator characteristic (ROC) curve assessed the diagnostic performance. Results: The VAS estimates of adherence correlated with VL. Various cutoffs for adherence were associated with VL suppression, demonstrating fair to moderate agreement through κ. Area under the curve (AUC) demonstrated that the ACASI-administered VAS strongly predicted VL suppression (AUC = 0.79). Discussion: The VAS administered by ACASI is viable for measuring highly active antiretroviral therapy (HAART) adherence among substance users. Its benefits as a screening instrument may make it useful for both clinical and research purposes.
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