A Prospective Study of Adherence and Virologic Failure in HIV-Infected Patients: Role of a Single Determination of Plasma Levels of Antiretroviral Medications

Abstract

This study explores the contribution of a single determination of plasma levels for measuring adherence by means of forecasting virologic failure. Adherence was measured by questionnaires, punctuality at appointments to withdraw drugs, and plasma levels. Virologic failure was considered when 2 detectable consecutive viral loads were observed in 2 consecutive determinations with at least 1 month between them. Univariant analysis, logistic regression, and receiver operating characteristic curves were carried out. In 29 cases, virologic failure was observed. The lowest incidence was found in patients considered adherent by plasma levels and highest in those who declared nonfulfillment. The combination of methods increased the association of the incidence of virologic failure with nonadherence. The use of questionnaires plus pharmacy information implies a gain in sensitivity and a slight loss of specificity. There is a high incidence of virologic failure in these patients and a strong link with their classification as nonadherent with methods such as questionnaires and pharmacy collection information. Plasma levels do not contribute much to the prediction of virologic failure.