Survival effects of ZDV, ddI, and ddC in patients with CD4 ≤50 cells/mm3

Seven major clinical trials for the treatment of HIV-infected individuals are investigated. The treatments used in these trials were zidovudine, dideoxyinosine, dideoxycytosine, and one combination for patients with CD4 cell counts < 500 cells/mm3. Patients in each trial are partitioned into two subgroups based on their baseline CD4 cell counts: patients with CD4 < or = 50 cells/mm3 and patients with CD4 > 50 cells/mm3. The difference between treatment effects, using survival as a measure of effect, within each subgroup is calculated separately for each trial; this difference is referred to as "subgroup response." For each trial the difference between the subgroup responses is calculated and standardized. A meta-analysis is conducted over all seven trials for the differences between subgroup responses; the consistency of responses is evaluated across all trials among patients within baseline CD4 subgroups. Based on the result of this meta-analysis we conclude that there is no evidence that the treatment effects in patients with CD4 < or = 50 cells/mm3 are different from those among patients with CD4 > 50 cells/mm3. This result is observed in patients with different antiviral experience and different baseline characteristics. Risk ratios as well as chi 2 statistics are used to quantify the response rates in different subgroups. Kaplan-Meier curves of survival for these trials are depicted for all patients and each subgroup separately. In most of the trials the Kaplan-Meier curves for the patients with CD4 < or = 50 cells/mm3 resemble those for all patients.