Background Knowledge of the patient’s adherence to antiretroviral treatment is extremely useful for monitoring HIV infection. However to measure this reliably is not easy. Several methods have been proposed to calculate adherence, each with its advantages and disadvantages.

Purpose To compare three of the available methods for assessing medicines adherence. To determine the factors associated with non-adherence to highly active antiretroviral treatment (HAART) in HIV/AIDS patients.

Materials and Methods Non-interventional and longitudinal study of patients diagnosed with HIV/AIDS who received HAART (May–June 2010). Three methods for evaluating medicines adherence were studied prospectively: Recording medicines dispensed (RD) from the Pharmacy Department; SMAQ (simplified medicines adherence questionnaire) interview; SMAE (scale for medicines adherence evaluation) interview. We recorded: demographic data (age, sex); years in treatment and daily doses of medicines.

Results 85.2% (104) of patients were males and mean age was 46 years (S8.9) with an average treatment time of 8.7 years (S4.6). 79% of patients have had a change in their medicines at some point in the treatment.

The percentage of patients with greater than 95% adherence was: 77.0% (RD), 62.3% (SMAQ) and 79.4% (SMAE).

By all measures of adherence patients with a single dose of medicine daily (SDM) were more adherent than twice-daily medicines (TDM): RD: 84% vs. 70% (p = 0.0781); SMAQ: 70.1% vs. 49.2% (p = 0.0189); ESPA: 85.9% vs. 69.2% (p = 0.0283) respectively. Patients who had been on HAART between 6–10 years had an adherence of 77.1%, while it was 65.8% for those treated 1–5 years and for patients with over 10 years of treatment, it was 40.8% (p = 0.002). Similar results with other measures.

Conclusions Since there is currently no ideal method to determine adherence to treatment, it is important to combine several methods depending on patient characteristics to obtain a measure as real as possible. Years with HAART reduces adherence and SDM regimens schedules appear to have better adherence than TDM regimens. This may affect treatment efficacy positively in the long term.

No conflict of interest.