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).