Objective: To investigate the relation between CD4 count and the immediate hazard of dying in patients receiving zidovudine (azidothymidine [AZT])-based antiretroviral therapy.
Setting: A research hospital that recruits patients from the entire United States.
Design: Retrospective analysis of a cohort of patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex participating in long-term zidovudine-based antiretroviral protocols.
Patients: Fifty-five patients with human immunodeficiency virus (HIV) infection and either AIDS or severe AIDS-related complex who were followed for as many as 4 years while they received antiretroviral therapy.
Measurements: CD4 counts were measured.
Main results: Ten patients are known to be alive and 1 was lost to follow-up. Of the 44 patients who are known to have died, the CD4 range was known within 6 months of death in 41. All but 1 of these 41 assessable deaths occurred in patients whose CD4 counts were known to have fallen below 50 CD4 cells/mm3 (P less than 10(-10)). The hazard of dying in the cohort ranged from 0 deaths/patient-month (95% CI, 0 to 0.008 deaths/patient-month) in patients with 200 or more CD4 cells/mm3 to 0.07 deaths/patient-month (CI, 0.050 to 0.094 deaths/patient-month) in patients with fewer than 50 CD4 cells/mm3. For the patients who died and whose cases were assessable, the mean of the last three CD4 counts obtained before death was 7.7 CD4 cells/mm3 (CI, 0.9 to 63.3 cells/mm3). The median survival of patients once their CD4 counts fell below 50 CD4 cells/mm3 was 12.1 months (CI, 7.2 to 19.4 months).
Conclusions: In a carefully followed cohort treated with zidovudine-based antiretroviral therapy, nearly all deaths occurred in patients with fewer than 50 CD4 cells/mm3. These findings may have implications in the monitoring of patients with AIDS and in the use of CD4 count as a clinical trials end point for the antiretroviral therapy of HIV infection.