The relative prognostic value of plasma HIV RNA levels and CD4 lymphocyte counts in advanced HIV infection

Objective: It has been suggested that the plasma HIV RNA level is a better predictor of AIDS and death than the CD4 lymphocyte count. We assessed whether the prognostic value of plasma virus levels was different according to the CD4 count. Design: Prospective cohort study of HIV-infected patients followed for a median of 2.91 years (range, 0.02-4.54). Setting: Department of Infectious Diseases at Rigshospitalet, Copenhagen, Denmark. Participants: A group of 255 HIV-infected individuals with an initial measurement of CD4 lymphocyte count and plasma HIV RNA. Main outcome measure: Survival time. Results: The plasma HIV RNA (median 101 410 copies/ml; range (range 200-7 200 000) and the CD4 lymphocyte count (median 250 cells x 10⁶/l; range 1-1247) were negatively correlated (Pearson r = -0.53; P < 0.00001). Of the 255 patients, 110 died during follow-up. Overall, a higher HIV RNA level was associated with increased risk of death, but the association was smaller in patients with lower. CD4 lymphocyte counts (test for interaction P < 0.0001). In patients with CD4 count below 50 cells x 10⁶/l the association between HIV RNA and risk of death was not statistically significant (relative hazard per 10-fold higher HIV RNA level was 1.53; P = 0.11; adjusted for age and CD4 count) while that between the CD4 count and risk of death was highly significant (relative hazard per 50% lower CD4 count 1.38; P = 0.005; adjusted for age and HIV RNA level). Conclusions: Patients were relatively lightly treated with antiretroviral drugs both before and during this study. In this situation, it appears that the HIV RNA level has a relatively weak association with risk of death in patients with advanced HIV infection and that the CD4 lymphocyte count is probably more useful in assessing prognosis.