CD4+ lymphocyte level and rate of decline as predictors of AIDS in intravenous drug users with HIV infection

Objective: To examine the relationship between rate of loss of CD4+ T lymphocytes and risk of AIDS in HIV-infected intravenous drug users (IVDU) enrolled in a methadone program in the Bronx, New York. Design: Serial CD4 percentages (CD4%) among lymphocytes before AIDS diagnosis were recorded at approximately 6-month intervals for 190 HIV-antibody-positive subjects. Methods: A nested case - control study was performed, in which all subjects who developed AIDS were compared with those who remained AIDS-free. The relationship between CD4% decline and AIDS risk was evaluated using proportional-hazards regression. Results: Analyses that used a single baseline CD4% measurement to adjust for CD4+ lymphocyte count suggested that both low (1-5 CD4% per semester) and high (> 5 CD4% per semester) rates of decline might be related to AIDS risk: relative risks were 1.83 and 1.44, although the 95% confidence intervals (Cl) included 1.0 in each case. Adjustment for current level of CD4% eliminated the association between low rates of CD4% decline and AIDS risk, but not that between high rates of decline and AIDS risk (adjusted relative risk, 1.80; 95% Cl, 0.57-5.70). Serial observations showed that a rate of decline of CD4% > 5 per semester was a significant predictor of AIDS risk after controlling for level of CD4% achieved (adjusted relative risk, 3.58; 95% Cl, 1.07-11.95). Conclusions: IVDU who develop AIDS have a greater rate of CD4 cell loss than subjects who remain AIDS-free. A low rate of CD4+ lymphocyte depletion is not an important predictor of the immediate onset of AIDS in HIV-infected IVDU, compared with CD4+ lymphocyte level, but a high rate of CD4+ decline can be.