Zidovudine use in AIDS-free HIV-1-seropositive homosexual men in the Multicenter AIDS Cohort Study (MACS), 1987-1989.

Zidovudine use data were examined in the Multicenter AIDS Cohort Study to determine (i) if the proportion of pre-AIDS participants (i.e., CD4+ cells less than 200/mm3 or AIDS-related complex) taking zidovudine is high enough to explain a slower than expected rise in AIDS incidence in U.S. homosexual men since mid-1987; (ii) which factors are associated with starting zidovudine and clinical trials of zidovudine; and (iii) if pre-AIDS patients, as a group, are being undertreated. Data on zidovudine use, clinical trial participation, and sociodemographic, clinical, and hematologic variables were collected every 6 months from 1,195 AIDS-free HIV-1-seropositive homosexual men from April 1987 to September 1989. Overall prevalence of zidovudine use rose from 3.6% in mid-1987 (visit 7) to 23% in mid-1989 (visit 11). Of those with less than 200 CD4+ lymphocytes/mm3, the prevalence of zidovudine use rose from 23% (24% if those taking zidovudine or placebo as part of a clinical trial are included) at visit 7 to 58% (69%) at visit 11. Of those with ARC, 20% (23%) were using zidovudine at visit 7 and 55% (65%) at visit 11. Although numbers were small, the advanced ARC participants (CD4+ cells less than 200/mm3 and two or more symptoms) reported the highest treatment rates (50, 78, 80, 60, and 74% at visits 7-11, respectively). By September 1989, 42% (31%) of those with CD4+ lymphocyte levels less than 200/mm3 were still not receiving zidovudine, suggesting that many high-risk, pre-AIDS individuals are being undertreated. To explore this finding further, we examined a range of sociodemographic, hematologic, and clinical variables to determine which factors best predicted initiation of zidovudine therapy outside of clinical trials. In multivariate analyses, CD4+ lymphocyte number was the most consistent predictor of initiation of therapy over all four study visits. For each 100 cells/mm3 deficit, the odds ratios were 2.3 (95% C.I. of 1.7-3.1) at visit 7 and 1.7% (95% C.I. of 1.4-2.0) at visit 11. Symptom status and education level were also associated with starting zidovudine, but not at all visits. The relatively low predictive power of the clinical variables raises and the possibility that nonclinical factors not measured in the MACS (drug cost, third-party insurance restrictions, and individual preferences) may play an important role in predicting zidovudine use. Finally, comparisons were made between seropositive participants starting clinical trials of zidovudine and the rest of the study population. No important differences were found in demographic or major clinical variables between clinical trial participants and zidovudine nonusers in this study.