Measuring adherence to ARVs among HIV-positive adolescents in Cameroon: a comparative assessment of self-report and medication possession ratio methods

INTRODUCTION: adherence to ARV medications has been shown to improve treatment outcomes in HIV positive patients. Given that ARV treatment is lifelong, adherence has become a critical issue as it may reduce over time. Measuring adherence is therefore imperative in programming. There are different methods of measuring adherence each with its advantages and disadvantages, depending on the context and the time. This study therefore compares two widely used adherence measurement scales in Cameroon, namely, the self-report and the medication possession ration (MPR) methods. METHODS: the study was done in some selected health facilities of the North West and South West regions of Cameroon among adolescents on ARV. The study was designed as an analytical cross-sectional study with a record review component and systematic random sampling was used to select the participants. Adherence was measured through self-report and the medication possession ratio. Adolescents with adherence levels of at least 95% were considered adherent. Viral load suppression was considered as having the most recent viral load suppression results of less than 1000 copies per ml. The kappa statistics of inter-rate agreement was used to ascertain the difference between adherence as measured by self-report and MPR. The difference in adherence between the two scales was also compared using Fischer´s exact test and p-values were reported. RESULTS: the study shows that adherence level using the self-report technique is 82.9% while that of MPR was 73.4%. When compared using the using Kappa statistics, there was substantial agreement between the two scales of 66% (p=0.54). The results of both self-report adherence and MPR were also compared with viral load suppression and the difference between viral load suppression and MPR was significant (p<0.01). The difference in adherence between viral load suppression and the self-report measure also showed to be significant (p<0.01). CONCLUSION: adherence from the self-report measure was higher than from MPR, but there was substantial agreement between the scales. Although there is no gold standard for adherence measurement, self-report or medication possession ratio could be used and complemented with laboratory markers like viral load counts.