Sustained Viral Suppression in HIV-Infected Patients Receiving Antiretroviral Therapy FREE

To the Editor: Antiretroviral therapy (ART) can be used to reduce human immunodeficiency virus (HIV) transmission.¹ For this treatment-as-prevention strategy to be effective, patients must adhere to ART and suppress plasma HIV RNA (viral load). Among patients receiving ART, 77% have been estimated to achieve viral suppression based on last recorded viral load, which may not accurately represent a patient's complete viral load history.² We examined the change in and determinants of sustained viral suppression over time in HIV-infected adults receiving ART.

We retrospectively evaluated consecutive HIV-infected adults who initiated care at 12 high-volume HIV clinics that are part of the HIV Research Network (HIVRN) and provided complete data between 2001 and 2010. Clinics are located in the Northeastern (n = 6), Midwestern (n = 1), Southern (n = 2), and Western (n = 3) sections of the United States and had a median panel size of 1598 patients in 2010. All patients were offered enrollment in the HIVRN, excluding 1-time consultations and incarcerated individuals; and 99% of patients participated. All clinics had institutional review board (IRB) approval; IRBs at some clinics required written informed consent, others waived the requirement because only existing deidentified data were collected. Data from patients' medical records were abstracted, quality assured, and assembled into a uniform database.

For patients receiving ART, we calculated the percentage who maintained viral loads of 400 copies/mL or lower throughout the entirety of each calendar year. Assays capable of detecting virus below 400 copies/mL were not in universal use at all clinics throughout the study period. Viral loads prior to and within the first 6 months after initial prescription of ART were not analyzed. We tested the association between patient sociodemographic characteristics and year receiving care using the χ² test of independence. Multivariate logistic regression was conducted to determine if the proportion of patients with sustained viral suppression changed over time, adjusting for sociodemographic characteristics. Because patients contributed data in multiple years, we used generalized estimating equations, clustered on patient, exchangeable working correlation, and robust standard errors to deal with the correlation across years for individual patients. Two-sided testing was used, with a P value of less than .05 considered significant. Statistical analyses were performed using Stata version 11.1 (StataCorp).

A total of 32 483 patients received care at the 12 clinics between 2001 and 2010 (Table 1). The percentage of patients receiving ART with sustained viral suppression increased from 45% (95% CI, 43%-47%) in 2001 to 72% (71%-73%) in 2010.

In a linear time trend, the proportion of patients with sustained viral suppression significantly increased (unadjusted odds ratio, 1.14 [95% CI, 1.13-1.14] per year; adjusted odds ratio, 1.14 [95% CI, 1.14-1.15]). Sustained viral suppression was lower for blacks and injection drug users during all 10 years. Older individuals and those with private insurance were more likely to have sustained viral suppression compared with younger patients and those with Medicaid, Medicare, or who were uninsured (Table 2).

The proportion of patients receiving ART with sustained viral suppression increased over the past decade. New drugs and combination fixed-dose tablets have enhanced the efficacy, safety, and tolerability of regimens. Better access to care and adherence to treatment may also have contributed to improved virologic suppression. Despite these improvements, in 2008-2010, only 64% to 72% of patients receiving ART had suppressed viral loads throughout the year. Our results differ from prior studies, which documented viral suppression in 77% to 87% of patients during this same period and used median or last recorded value to measure viral load.^2- 4

Lower sustained viral suppression among younger patients, blacks, injection drug users, and those without private insurance may represent poor adherence to treatment, drug resistance, or drug intolerance or toxicity.^5- 6

This study is limited by its retrospective nature and inability to measure adherence to treatment. While our findings may not be generalizable to all HIV-infected patients receiving ART, they are relevant for HIV treatment-as-prevention programs because suboptimal viral suppression may lead to worse clinical outcomes and increased costs.