Antiretroviral Therapy Cohort Collaboration : prognostic importance of initial response in HIV-1 infected patients starting potent antiretroviral therapy : analysis of prospective studies

Background: We examined whether the initial virological and immunological response to highly active antiretroviral treatment (HAART) is prognostic in patients with HIV-1 who start HAART. Methods: We analysed 13 cohort studies from Europe and North America including 9323 adult treatment-naive patients who were starting HAART with a combination of at least three drugs. We modelled clinical progression from month 6 after starting HAART, taking into account CD4 count and HIV-1 RNA measured at baseline and 6 months. Findings: During 13 408 years of follow-up 152 patients died and 874 developed AIDS or died. Compared with patients who had a 6-month CD4 count of fewer than 25 cells/μL, adjusted hazard ratios for AIDS or death were 0.55 (95%CI 0.32-0.96) for 25-49 cells/μL, 0.62 (0.40-0.96) for 50-99 cells/μL, 0.42 (0.28-0.64) for 100-199 cells/μL, 0.25 (0.16-0.38) for 200-349 cells/μL, and 0.18 (0.11-0.29) for 350 or more cells/μL at 6 months. Compared with patients who had a 6-month HIV-1 RNA of 100 000 copies/mL or greater, adjusted hazard ratios for AIDS or death were 0.59 (0.41-0.86) for 10 000-99 999 copies/mL, 0.42 (0.29-0.61) for 500-9999 copies/mL, and 0.29 (0.21-0.39) for 6-month HIV-1 RNA of 500 copies/mL or fewer. Baseline CD4 and HIV-1 RNA were not associated with progression after controlling for 6-month concentrations. The probability of progression at 3 years ranged from 2.4% in the patients in the lowest-risk stratum to 83% in patients in the highest-risk stratum. Interpretation: At 6 months after starting HAART, the current CD4 cell count and viral load, but not values at baseline, are strongly associated with subsequent disease progression. Our findings should inform guidelines on when to modify HAART.