VOLUNTARY CONFIDENTIAL HIV TESTING OF STD PATIENTS IN SWITZERLAND, 1990-5 - HIV TEST REFUSERS CAUSE DIFFERENT BIASES ON HIV PREVALENCES IN HETEROSEXUALS AND HOMO BISEXUALS/

Objectives: To monitor the prevalence of HIV infection among heterosex ual and male homo/bisexual STD patients and assess the effect of HIV t est refusers on the HIV prevalences. Methods: A voluntary confidential HIV test was offered to all people diagnosed with an STD at the Swiss Network of Dermatovenereology Policlinics (SNDP) between July 1990 an d June 1995. Anonymous sociodemographic and behavioural information wa s collected for each patient regardless of whether s/he accepted or re fused the HIV test. Results: The prevalence of HIV was 1.6% among hete rosexuals and 22.4% homo/bisexual men and remained stable between July 1990 and June 1995. Refusal rates were 17.5% among heterosexuals and 16.0% among homo/bisexual men and did not change significantly over ti me. To assess the potential effect of HIV test refusers on the monitor ed HIV prevalences, we analysed test refusers by multivariate logistic regression. hmong heterosexuals, refusal rates were significantly hig her among patients with relatively low risk behaviours (patients repor ting 0-1 sexual partners in the previous 6 months) while among homo/bi sexual men they were significantly higher in those with high risk beha viours (patients reporting 10 or more sexual partners in the previous 6 months). Conclusions: We found high and stable HIV prevalences among patients treated for an STD at the SNDP. It appears that HIV test ref users biased HIV prevalences among heterosexuals and homo/bisexual men in different directions: in heterosexuals HIV prevalences were overes timated and in homo/bisexuals they were underestimated. A regular anal ysis of the characteristics of HIV test refusers should be an integral part of surveillance systems which use voluntary confidential HIV tes ting.