For purposes

of analysis, race/ethnicity was categorized as African American and non-African American and HIV risk factor as injecting drug use (IDU) and non-IDU. Calendar time for the date of HAART initiation was categorized as 1997–1998, 1999–2002 and 2003–2006, reflecting milestones in antiretroviral development learn more (Food and Drug Administration approval of efavirenz in September 1998 and of atazanavir in June 2003). Virological and CD4 responses to HAART were determined using the single measurements made between 120 and 180 but closest to 180 days after HAART initiation. Virological responders were defined as having a decrease in HIV-1 RNA of ≥1 log10 HIV-1 RNA copies/mL or suppression

below the detection limit of the assay. Their HIV-1 RNA levels may subsequently have risen after 180 days. Nonresponders did not achieve a drop in HIV-1 RNA of ≥1 log10 copies/mL at 180 days. For analysis purposes, CD4 response was categorized as being above or below the median change in CD4 seen among virological responders. Of the 1685 patients initially considered for inclusion, 300 were excluded because of insufficient virological data. Number of hospital admissions per time period see more was the primary study outcome. Counts of distinct hospital admission dates were obtained, beginning with the period from 180 days prior to HAART initiation to the day of HAART initiation. Patients were then followed for 365 days after HAART initiation, with hospitalization counts assessed in time periods of 1–45, 46–90, 91–180 and 181–365 days after initiation. For persons enrolling <180 days prior to HAART initiation, the clinic enrolment date was the start of observation. Observation ended at the sooner of (1) 365 days after HAART initiation, (2)

death, (3) regimen change (including complete HAART discontinuation or of any change from the initial regimen except for dosing changes), or (4) study discontinuation as a result of voluntary withdrawal or loss to follow-up. The primary reason for each hospitalization was assessed through International Classification of Diseases, Ninth Revision (ICD-9) codes and physician chart abstraction. Hospitalizations related to clinical trials (140) were excluded from all analyses. Using a method that has twice been validated in our cohort with over 95% accuracy compared with chart review [5,15], the first of the top three ICD-9 codes that was neither 042 (AIDS) nor 112.0 (thrush) was defined as the primary diagnosis.