July 7, 2003
Between January 1996 and May 2001, 289 patients from the Cape Town AIDS Cohort, a group of HIV-positive individuals presenting to the University of Cape Town HIV clinics, were recruited. There was no dedicated adherence counseling service, structured adherence support or formal adherence intervention as part of treatment.
Adherence was assessed using clinic-based pill counts and pharmacy refill data over a period of 48 weeks. All ART was dispensed from the single study site. Tablets were usually dispensed in multiples of 30, whereas visits were booked in multiples of 28 days. Patients were instructed to return all medication bottles and unused pills at each study visit, but were not told that the returns were to be counted. Adherence was calculated using the formula: (sum of tablets dispensed -- sum of tablets returned)/(total tablets prescribed over the 48-week study interval).
Patients not completing at least 30 days of ART were excluded from the analysis. Patients who failed to bring any tablet returns over the study period were assigned a 0 percent adherence value (n=8). For those who withdrew from the study before 48 weeks, the last data available were brought forward to be included in the 48-week analysis.
Regimens containing protease inhibitors were used by 120 (41.5 percent) patients. Ninety-four (32.5 percent) patients received non-nucleoside based regimens, 30 (10.4 percent) took triple nucleoside regimens, and 45 (15.6 percent) of the patients received dual nucleoside reverse transcriptase inhibitors. Fifty-five percent took more than 10 tablets a day, and 41 percent had dietary restrictions related to antiretroviral therapy.
Median adherence was 93.5 percent (mean, 87.2 percent). Sixty-three percent of patients maintained adherence of 90 percent or greater. There was no significant difference in adherence to protease regimens compared to non-nucleoside based regimens. Of those who reached 48 weeks of therapy (n=242), 66.1 percent had a viral load of less than 400 HIV RNA copies/ml. This included 70.9 percent of those on triple therapy and 41 percent of those on dual therapy.
Three times daily dosing [risk ratio (RR), 3.07], speaking English (RR, .41), and age (RR, .97) were independent predictors of incomplete adherence. Socioeconomic status, sex and HIV stage did not predict adherence. Independent predictors of virologic failure included baseline viral load (RR, 2.57) and three times daily dosing (RR, 2.64), incomplete adherence (RR, 1.92), age (RR, .96) and dual nucleoside therapy (RR, 2.69).
"This level of adherence and viral suppression is similar to or better than that reported in most observational and clinical trial cohorts in developed countries," the authors concluded. "Living in poor socio-economic circumstances ... did not impact on adherence to therapy," they wrote, and it "should not be used as a limitation to ART access."
06.13.03; Vol. 17; No. 9: P. 1369-1375; Catherine Orrell; David R. Bangsberg; Motasim Badri; Robin Wood