Fifty-four participants were enrolled in the adherence sub-study, and 46 adherence sub-study participants contributed at least one MEMS/VAS paired reading. Fifty Steps Study participants on ART were not included in the sub-study because they used other clinics, used other pharmacies, or were started on ART after the sub-study slots were filled. No differences were found in gender, age, race/ethnicity, education level, insurance level, or HIV risk factor between participants in the sub-study and these 50 Steps Study participants. The majority of the 46 adherence sub-study participants were male, between 30 and 50 years old, Hispanic, had no high school degree, and had low incomes (). Twenty-six patients (57%) were on an NNRTI and 20 (43%) were on a boosted PI. The median baseline CD4 count was 75 K/mm3 (IQR 22,197 K/mm3) and the median baseline HIV viral load was 5.44 log10 c/mL (IQR 5.16, 5.78). Detailed characteristics of the participants are shown in .
Characteristics and self-reported adherence of study participants enrolled in the STEPS adherence sub-study in Houston, TX
Mean MEMS adherence during 28-day intervals with paired VAS data was 84.7% (SD 35.6) with a median of 89.2% (IQR 78.3, 99.1). Mean pharmacy adherence over the length of the study was 84.5% (SD 15.1) with a median of 92.9% (IQR 80.7, 98.2). Mean VAS score over the same time period was 95.4% (SD 11.9) with a median of 98.3% (IQR 92.0, 99.8). Mean AACTG 4-day self-report adherence was 95.8% (SD 17.2), while the median was 100% (IQR 93.8, 100). The qualitative single-item measure had a mean of 87.6% (SD 28.2) and a median of 95.0% (IQR 75.0–100.0).
The Spearman correlation coefficient between pharmacy and MEMS adherence over the 18-month time period was 0.30 (95% CI 0.14, 0.44; p<0.01). The correlation coefficient between VAS and MEMS adherence overall was 0.37 (95%CI 0.22, 0.50; p<0.01), and ranged between 0.18 and 0.53 at each time point (). The VAS had a correlation coefficient of 0.34 (95% CI 0.21, 0.46; p<0.01) with pharmacy data over the same time period (). The qualitative single-item measure had a lower, but still statistically significant correlation coefficient with MEMS data (0.24; 95% CI 0.08, 0.38; p<0.01) and with pharmacy data (0.32; 95% CI 0.18, 0.44; p<0.01; ). The correlation coefficient of the AACTG 4-day self-report measure with MEMS data was 0.32 (95% CI 0.16, 0.45; p<0.01); with pharmacy data it was 0.28 (95% CI 0.14, 0.41; p<0.01). The VAS had a correlation coefficient of 0.58 (95% CI 0.50, 0.64; p<0.01) with the qualitative single-item measure and 0.52 (95% CI 0.44, 0.59; p<0.01) with the AACTG measure. The qualitative single-item measure had a correlation coefficient of 0.45 (95% CI 0.36, 0.53; p<0.01) with the AACTG.
Spearman correlation coefficients of visual analogue scale (VAS) to MEMS and pharmacy data over time among patients in the STEPS adherence sub-study
Spearman correlation coefficients of VAS, AACTG and Qualitative Single Item Measure to MEMS and pharmacy data over all follow-up time among patients in the STEPS adherence sub-study
The correlation coefficients of VAS to MEMS data in various subpopulations are shown in . The correlations were statistically significant in most subpopulations examined. VAS adherence in participants who did not need assistance to complete the VAS had a correlation coefficient of 0.28 (95% CI 0.13, 0.42, p<0.01) with the MEMS data; in those participants who needed help with percentages, the correlation was 0.67 (95% CI −0.07, 0.93, p=0.07), while in participants who needed total assistance, the correlation was 0.33 (95% CI −0.49, 0.84, p=0.43). Participants who self-administered the VAS had a correlation coefficient of 0.49 (95% CI 0.25, 0.67, p<0.01) with the MEMS data, while those participants who did not had a correlation coefficient of 0.29 (95% CI 0.11, 0.45, p<0.01). When we restricted the analysis to the participant’s first encounter with the VAS, the correlation coefficient with MEMS for self-administered VAS was 0.49 (95% CI 0.25, 0.67, p=<0.01; 53 measurements), while for the interviewer-administered VAS the correlation was 0.29 (95% CI 0.11, 0.45, p<0.01; 115 measurements). We could not calculate correlations of adherence to viral load because all patients achieved a viral load of <400 copies/mL by 12 months.
Spearman correlation coefficients of visual analogue scale to MEMS data over all follow up time in various patient subpopulations