PERFORMANCE OF A RAPID, ON-SITE HUMAN-IMMUNODEFICIENCY-VIRUS ANTIBODY-ASSAY IN A PUBLIC-HEALTH SETTING

Rapid, on-site human immunodeficiency virus (HIV) testing has the pote ntial to improve the delivery of prevention services in publicly funde d counseling and testing sites, The Single Use Diagnostic System (SUDS ) HIV-1 is the only rapid enzyme immunoassay (EIA) approved for diagno stic use in the United States, To evaluate the feasibility of using SU DS in public clinics and to validate the test's performance in a publi c health laboratory, we conducted blinded SUDS testing on plasma sent for HIV testing, From 19 March through 30 June 1993, 1,923 consecutive samples from a sexually transmitted diseases clinic and an HIV counse ling and testing clinic were tested on site,vith SUDS. Tests done in t he first two weeks with a malfunctioning centrifuge (n = 402) and thos e done when there were excessively high temperatures in the laboratory (n = 53) were analyzed separately, Of 1,466 tests, 39 were positive b y both SUDS and EIA (with Western blot [immunoblot] confirmation) and 7 were SUDS positive and EIA negative, Western blotting was used as th e ''gold standard'' to adjudicate these discrepancies, There were no S UDS-negative and EIA-positive tests, Compared with that of EIA (with W estern blot confirmation), the sensitivity of SUDS was 100% (95% confi dence interval, 88.8 to 100%) and the specificity was 99.5% (95% confi dence interval, 98.9 to 99.8%), The positive predictive value of SUDS was 88% in the STD clinic and 81% in the HIV counseling and testing cl inic. There was a 7.7-fold increase in false positives, from 0.48 to 3 .7%, when there was inadequate centrifugation and when the temperature exceeded the manufacturer's recommendations. Rapid, on-site HIV testi ng by the SUDS assay is feasible and practical in public health settin gs. The test can be performed accurately, at reasonable cost, and with in the time frame of a typical clinic visit, Caution should be used, h owever, as two conditions adversely affected the accuracy of this test : inadequate specimen preparation and elevated temperature.