Study of the Validity of a Questionnaire to Assess the Adherence to Therapy in Patients Infected by HIV

Abstract

The purpose of our study was to examine the validity of a questionnaire to detect nonadherence in HIV-infected patients under antiretroviral treatment. This was a cross-sectional study to validate a diagnostic test. Participants consisting of 242 HIV-infected patients were elected by consecutive sampling in a hospital in Madrid. The validation standard was the pharmacy dispensing records with the cut point being 80% and 90% of delivered drugs. Sensitivity (S), specificity (SP), positive predictive value (PPV), and positive likelihood ratio (PLR) of the questionnaire were estimated. The mean age of the participants was 36.2 years old (SE 0.42), 55% were men, and 68.2% had used parenteral drugs. Eighty-three patients (34.3%) did not reach 80% of the prescribed dose and 129 patients (53.3%) did not reach 90%. In the 80% group, S was 25.3% (95% CI, 16.7%-36.2%),SP was 86.2% (95% CI, 79.6%-90.9%), PPV was 48.9% (95% CI, 33.5%-64.3%), and the PLR was 1.83 (95% CI, 1.07-3.13). In the 90% group, the S was 19.4% (95% CI, 13.4%-27.4%), SP was 84.0% (95% CI, 75.7%-90.0%), PPV was 58.1% (95% CI, 42.4%-72.6%), and PLR was 1.22 (95% CI, 0.70-2.12). The proposed questionnaire is not a reliable diagnostic method to detect nonadherence. It should only be incorporated into the daily clinical practice along with other methods of nonadherence measurement.