Quantitative HIV-1 RNA as a marker of clinical stability and survival in a cohort of 302 patients with a mean CD4 cell count of 300 x 10⁶/l

Objective: To analyse plasma HIV-1 RNA levels as a marker of clinical stability and survival in a cohort of HIV-infected patients whose time of seroconversion is unknown. Design: Retrospective cohort study. Setting: Retrovirology laboratory and AIDS Unit in a teaching hospital. Patients: A total of 916 samples from 302 patients, most on antiretroviral therapy, were analysed. Mean initial CD4 cell counts and HIV-1 RNA were 299 x 10⁶/l (range: 0-1600) and 134 261 copies/ml (range: < 200-4 300 000), respectively. Sixty-six cases had been diagnosed previously with AIDS. Methods: Analysis of progression to AIDS and survival, according to initial and longitudinal viral load (VL) and CD4 cell count measurements was performed by Kaplan-Meier test. Relative risks were calculated by Cox's proportional hazards model. Results: During a mean follow-up of 444 ± 309 days, 29 patients developed AIDS and 21 died. Relative risk (RR) of progression related to the group with VL < 35 000 was: 10.4 when CD4 ≤ 250 x 10⁶/l and VL ≤ 35 000 (P = 0.001); and 45.3 when CD4 < 250 x 10⁶/l and VL ≤ 35 000 (P < 0.0001). Cumulative probability of progression was: 0%, 0% and 12.3%, at the first, second and third year respectively, for patients with all their sequential VL determinations < 60 000; and 13.3%, 34.7% and 79.3% for patients who did not maintain VL values always < 60 000 (RR = 23; P < 0.0001). The minimum value of VL that reached statistical significance for the survival analysis was 100 000 copies/ml (P < 0.0001). Conclusions: VL ≤ or < 35 000 is a better discriminant for progression than a CD4 cell count ≤ or < 250 x 10⁶/l. Sequential VL determinations < 60 000 are associated with a better prognosis.