Recommended method for health services to determine adherence to antiretroviral therapy: a comparison of three models

Abstract

The medication possession ratio (MPR) method is commonly used for the determination of antiretroviral medication adherence. However, different ways of calculating MPR and methodological issues hinder the interpretation of the results and the reproducibility of the method. Thus, this study used three different models of MPR calculation and aimed to identify the one that best represents the situation of patient adherence. The results show that there was a statistically significant difference between the adherence rates determined by the three models, which indicates the need to specify the parameters used for calculation in the MPR method. However, the models individually were found to be related to viral suppression, but none of them had a greater effect than the other in this regard. The model that used residual medication (RM) and a fixed period of analysis allowed for a more precise identification of the number of doses that the patient used when compared to the others. Health services should avoid the application of the model using a variable analysis period. This study found that RM and the period of analysis considered are the main influencing factors in the accuracy of adherence results when the MPR method is used.