CD4 and AIDS: A higher CD4 cell count was always associated with a reduced risk of a new AIDS event or death; with a hazard ratio per 100 cells/μl (95% CI) of: 0.35 (0.30–0.40) for counts <200 cells/μl, 0.81 (0.71–0.92) for counts 200 to <350 cells/μl, 0.74 (0.66–0.83) for counts 350 to <500 cells/μl, and 0.96 (0.92–0.99) for counts ≥500 cells/μl.