Comparison of voluntary and blinded human immunodeficiency virus type 1 (HIV-1) seroprevalence surveys in a high prevalence sexually transmitted disease clinic population.

To compare the seroprevalence of and risk factors for human immunodeficiency virus infection (HIV) among patients attending a public sexually transmitted disease clinic, the authors conducted both voluntary and blinded seroprevalence surveys between June 1989 and August 1990. For the voluntary survey, every twenty-fifth patient attending the clinic for a new problem was invited to receive anonymous testing for HIV antibody. For the blinded survey, sera obtained for syphilis serologies from 2,297 (86%) of the 2,682 patients attending the clinic for a new problem were tested for HIV antibody after all personal identifiers were removed. Of the 946 eligible patients, 631 (66.7%) agreed to participate in the voluntary survey. Black men were significantly less likely to participate than other men and women (p < 0.0001). The prevalence of HIV antibody was 25% greater in the blinded survey than in the voluntary survey (15.2% and 11.4%, respectively, p < 0.05). This difference was due primarily to black homosexual/bisexual men, who had a 12.7-fold greater risk of HIV infection in the blinded survey than in the voluntary survey. These results suggest that blinded seroprevalence surveys may provide a better prevalence estimate of HIV infection than voluntary surveys. The greater risk for HIV infection observed among homosexual and bisexual black men, who were tested only in the blinded serosurvey, suggests that efforts to increase voluntary testing for HIV infection in this group should be developed.