COMPOSITE RISK SCORE FOR KAPOSI-SARCOMA BASED ON A CASE-CONTROL AND LONGITUDINAL-STUDY IN THE MULTICENTER AIDS COHORT STUDY (MACS) POPULATION

The possibility that an agent in addition to human immunodeficiency vi rus type 1 may be involved in the etiology of Kaposi's sarcoma in acqu ired immunodeficiency syndrome (AIDS) patients was investigated betwee n 1984 and 1992 in this nested case-control analysis from the Multicen ter AIDS Cohort Study (MACS) of homosexual and bisexual men. A total o f 316 cases of Kaposi's sarcoma were identified and compared with 51 0 participants with AIDS and no evidence of cancer. More of the Kaposi' s sarcoma cases were from Los Angeles and used a higher number of recr eational drugs. The Kaposi's sarcoma cases were also more active sexua lly. There was a dose-response relation between Kaposi's sarcoma and t he number of sexual partners, with an odds ratio of 2 between the most and least sexually active subgroups. The odds ratio for Kaposi's sarc oma increased to 4.18 (95% confidence interval 1.29-14.1) in the prese nce of a history of five infections. Hepatitis and gonorrhea contribut ed the most to this relation. The various observed odds ratios did not change after multivariate adjustment for the other risk factors. A mo del was developed combining all predictive associations into a composi te risk score ranging from one to 12 and based on history of infection s, sexual activity, use of poppers/nitrites, and having had sexual par tners from the West Coast of the United States. The subgroup with the highest scores, compared to the subgroup with the lowest score, had an odds ratio of 8.93 (95% confidence interval 3.21-30.44) for Kaposi's sarcoma. A longitudinal proportional hazards analysis among all 2,190 human immunodeficiency virus type 1-seroprevalent men at study entry, based on this risk score and CD4 cells at baseline, confirmed these fi ndings. Identifying these specific subgroups that are at high and low risk for Kaposi's sarcoma will help future investigations to be more f ocused in their search for an additional etiologic factor for Kaposi's sarcoma in AIDS.