Monitoring Medication Adherence by Unannounced Pill Counts Conducted by Telephone: Reliability and Criterion-Related Validity

Background: Although demonstrated valid for monitoring medication adherence, unannounced pill counts conducted in patients' homes are costly and logistically challenging. Telephone-based unannounced pill counts offer a promising adaptation that resolves most of the limitations of home-based pill counting. Purpose: We tested the reliability and criterion-related validity of a telephone-based unannounced pill count assessment of antiretroviral adherence. Method: HIV-positive men and women (N = 89) in Atlanta, Georgia, completed a telephone-based unannounced pill count and provided contemporaneous blood specimens to obtain viral loads; 68 participants also received an immediate second pill count conducted during an unannounced home visit. Results: A high degree of concordance was observed between the number of pills counted on the telephone and in the home (intraclass correlation [ICC] = .981, p < .001) and percent of pills taken (ICC = .987, p < .001). Adherence obtained by the telephone count and home count reached 92% agreement (Kappa coefficient = .94). Adherence determined by telephone-based pill counts also corresponded with patient viral load, providing evidence for criterion-related validity. Conclusion: Unannounced telephone-based pill counts offer a feasible objective method for monitoring medication adherence.