Racial Differences in Response to Antiretroviral Therapy

In the United States, blacks infected with human immunodeficiency virus (HIV) have higher rates of virologic failure on antiretroviral therapy (ART) and of death compared to white individuals. Up to this point, it has been difficult to separate social factors such as demographics, socioeconomic influences, and poor compliance with medications from biological factors such as suboptimal response to ART.

A new study published recently in the journal Clinical infectious Diseases,¹ combined data from 5 large randomized trials from the AIDS Clinical Trials Group (ACTG). Because patients were randomly assigned to ART in these studies, access to treatment as a confounder was eliminated allowing examination of racial differences in biological responses to ART.

The analysis included 2495 ART-naive patients enrolled in ACTG trials, the median follow-up was 129 weeks and was similarly distributed by race; 43% of participants had more than 3 years of follow-up.¹ Patients were randomized to 15 different initial ART treatment regimens. Criteria for virologic failure were failure to decrease viral load: by 0.5 log copies below baseline at week 4; by 1.0 log copies below baseline at week 8; to ≤1000 copies at week 16; or, to ≤200 copies at week 24.

Overall time to virologic failure was significantly shorter for blacks compared with whites (P <.001); the 3-year cumulative probability of virologic failure was 45% (95% confidence interval [CI], 42% to 48%) for blacks compared with 32% (95% CI, 29% to 35%) for whites.¹ Different types of ART combinations did not affect this outcome. Black ethnicity continued to be an independent risk factor for virologic failure after adjustment for confounders such as younger age, higher pretreatment viral load, lower pretreatment CD4 cell count, hepatitis C virus co-infection, less education, and recent medication non-adherence.

The investigators conclude that the consistency of their observation over a range of regimens suggests that it may be driven by unmeasured social factors, although biological factors cannot be ruled out. Future studies are required to address the reasons behind outcome disparities as well as the necessary interventions to address them.

For primary care physicians who care for HIV-infected patients, awareness of these results may help provide insight into observed poor treatment results.


Reference
1. Ribaudo HJ, Smith KY, Robbins GK, et al. Racial differences in response to antiretroviral therapy for HIV infection: an AIDS Clinical Trials Group (ACTG) study analysis. Clin Infect Dis. 2013 Oct 10. [Epub ahead of print] (Abstract)