Correlation between lamivudine plasma concentrations and patient self-reported adherence to antiretroviral treatment in experienced HIV patients

BACKGROUND: Adherence to antiretroviral treatment (ART) is important to achieve treatment success in human immunodeficiency virus (HIV)-infected patients. Most HIV clinics apply the patient self-report (PSR) method. However, the reliability of this method in experienced HIV patients remains questionable. PURPOSE: To validate the PSR method for measuring adherence to ART using lamivudine (3TC) plasma concentrations in experienced HIV patients. METHODS: The study was conducted in Dar Es Salaam and involved 220 patients who were receiving ART services at HIV clinics for more than 12 months. Self-reported adherence information to ART was obtained on the day of HIV clinic visit. The patients were asked to mention the number of doses missed within the past 7 days. In addition, blood samples (2 mL) were collected from each patient on the same day. The blood samples were determined for 3TC plasma concentrations. The target 3TC plasma concentration as indicator concentration for adherent patients was determined in 20 patients who took their evening dose of antiretrovirals under supervision. The blood from these patients was drawn 3 hours after drug administration. RESULTS: Complete drug levels of 3TC and self-reported adherence data was obtained in 200 treatment-experienced HIV patients. Lamivudine plasma concentrations obtained in these patients ranged between 0.02–17.36 μg/mL. The mean time from dose administration to blood drawing was 3.1 ± 1.2 hours with coefficient of variation >39%. The mean 3TC plasma concentration obtained in 20 patients who took their antiretroviral dose under supervision was found to be 0.67 ± 0.46 μg/mL, range 0.25–2.33 μg/mL. As many as 82.5% of experienced HIV patients had PSRs in agreement with their 3TC plasma concentrations. CONCLUSION: PSR adherence is still a valid method for ascertaining adherence to ART in treatment-experienced HIV patients.