Validation of a New Three-Item Self-Report Measure for Medication Adherence

Abstract

Few self-report measures of medication adherence have been rigorously developed and validated against electronic drug monitoring (EDM). Assess the validity of the 3-item self-report scale by comparing it with a contemporaneous EDM measure. We conducted an observational study in which adherence assessments were done monthly for up to 4 months for 81 patients with HIV who were taking antiretroviral medications. We report results for both HIV antiretroviral medications, and also for other, non-HIV-related medications. Raw and calibrated self-report adherence measures, electronic drug monitoring adherence measures, and sociodemographic variables. The mean age of patients was 46 years, 37 % were female, 49 % had some education beyond high school, 22 % were Black, and 22 % were Hispanic. Cronbach's alphas for the 3-item scale for HIV and non-HIV medications were 0.83 and 0.87, respectively. The mean differences (raw/uncalibrated self-report scale minus EDM) for HIV and non-HIV medications were 7.5 and 5.2 points on a 100-point scale (p < 0.05 for both). Pearson correlation coefficients between the calibrated 3-item scale and the EDM for HIV and non-HIV medications were 0.47 and 0.59, respectively. The c-statistics for the ROC curves for the calibrated scale, using cut-offs of 0.8 and 0.9 for the EDM gold standard measure to define non-adherence, were between 0.74 and 0.76 for HIV and non-HIV medications. This 3-item adherence self-report scale showed good psychometric characteristics and good construct validity when compared with an EDM standard, for both HIV and non-HIV medications. In clinical care it can be a useful first-stage screener for non-adherence. In clinical research and quality improvement settings it can be a useful tool when more complex and expensive methods such as EDM or pharmacy claims are impractical or unavailable.

Keywords: HIV; Highly active antiretroviral therapy; Medication adherence; Patient compliance; Self-report.

Figures

Fig. 1

Comparison of raw 3-item self-report scale with EDM measure for HIV ARVs (N = 431) and non-ARVs (N = 195). The 95 % CI’s use mixed models to account for the clustering in the data structure

Fig. 2

In this figure, this histogram shows the distribution of item scores for each of the 3 self-report adherence scales (including both HIV and non-HIV medications). The blue line shows the the score given to each response category using a linear, equal interval, zero to 100 approach, and the red line shows the score calibrated to the EDM measure (Color figure online)

Fig. 3

This figure shows mean scores for the raw scale, the calibrated scale, and the EDM measure for HIV ARVs and non-ARVs, respectively