Antiretroviral Refill Histories as a Predictor of Future Human Immunodeficiency Virus Viremia

Background: The use of adherence measures as markers for virologic failure (VF) has been studied. Yet, there is currently no single adherence metric recommended for VF. Antiretroviral prescription refill histories, for people living with human immunodeficiency virus (HIV), are readily accessible and can be easily quantified to an estimated adherence level. Methods: Participants from a Midwestern US HIV clinic were retrospectively evaluated from 2018 to 2020. Refill histories (RH) and last HIV RNA for each participant were abstracted for each study year. RH were quantified as a percentage of days covered (PDC) and VF was defined as HIV RNA >200 copies/mL. PDC values were matched with subsequent year HIV RNA (matched pair). Sample t test were used to compare mean PDC level by viral suppression status and generalized estimating equations models were used to determine the predictability of PDC level for VF. An optimal PDC threshold for VF was determined using receiver operating characteristic curve analysis and Youden index. Results: A total of 1056 participants contributed to 1923 matched pairs (PDC/HIV RNA); mean age was 48.3 years, 24% women, and 30.6% Black. PDC levels differed significantly based on dichotomized HIV RNA (2018-2019: >200: 40% [95% confidence interval {CI}, 33%-46%] vs ≤200: 85% [95% CI, 84%-87%], P <. 0001; 2019-2020: >200: 45% [95% CI, 38%-51%] vs ≤200: 87% [95% CI, 86%-89%], P <. 0001). Based on the Youden index value of 0.66 (sensitivity 0.77, specificity 0.89), the optimal PDC threshold predictive of VF was 52%. Conclusions: Lower antiretroviral therapy (ART) adherence levels were predictive of future VF when PDC ≤52%.