Antiretroviral Adherence Level Necessary for HIV Viral Suppression Using Real-World Data

Abstract

Background: A benchmark of near-perfect adherence (≥95%) to antiretroviral therapy (ART) is often cited as necessary for HIV viral suppression. However, given newer, more effective ART medications, the threshold for viral suppression may be lower. We estimated the minimum ART adherence level necessary to achieve viral suppression.

Settings: The Patient-centered HIV Care Model demonstration project.

Methods: Adherence to ART was calculated using the proportion of days covered measure for the 365-day period before each viral load test result, and grouped into 5 categories (<50%, 50% to <80%, 80% to <85%, 85% to <90%, and ≥90%). Binomial regression analyses were conducted to determine factors associated with viral suppression (HIV RNA <200 copies/mL); demographics, proportion of days covered category, and ART regimen type were explanatory variables. Generalized estimating equations with an exchangeable working correlation matrix accounted for correlation within subjects. In addition, probit regression models were used to estimate adherence levels required to achieve viral suppression in 90% of HIV viral load tests.

Results: The adjusted odds of viral suppression did not differ between persons with an adherence level of 80% to <85% or 85% to <90% and those with an adherence level of ≥90%. In addition, the overall estimated adherence level necessary to achieve viral suppression in 90% of viral load tests was 82% and varied by regimen type; integrase inhibitor- and nonnucleoside reverse transcriptase inhibitor-based regimens achieved 90% viral suppression with adherence levels of 75% and 78%, respectively.

Conclusions: The ART adherence level necessary to reach HIV viral suppression may be lower than previously thought and may be regimen-dependent.

FIGURE 1.

*PDC, proportion of days covered; † Φ is the cumulative distribution function for the standard normal distribution; ‡INSTI, integrase inhibitor; §NNRTI, nonnucleoside reverse transcriptase inhibitor; ‖PI, protease inhibitor; ¶INSTI-, NNRTI-, and PI-based regimens each included one medication of the main component and 2 nucleoside reverse transcriptase (NRTI) drugs as the “backbone” of the therapy; **includes all regimens not categorized as an INSTI-, NNRTI-, or PI-based. The horizontal dash lines represent the 90% benchmark for viral suppression and the dotted vertical lines represent the PDC level at which 90% of HIV viral load tests were suppressed (HIV RNA <200 copies/mL).