CONCORDANCE OF PCR AND ANTIBODY RESULTS FROM HIV TESTING OF INJECTINGDRUG-USERS

Standard HIV-1 testing relies on the enzyme immunoassay (EIA) for dete cting antibodies specific to HIV-1. This technique may misclassify per sons as HIV-1-negative in instances where testing follows infection bu t precedes development of antibody to HIV-1. To evaluate the occurrenc e of HIV infection in the absence of positive antibody, polymerase cha in reaction (PCR) for viral DNA in the blood has been applied. Researc h comparing these two testing techniques has generally focused on popu lations of homosexual and bisexual men. This study compares PCR and an tibody testing of 337 injecting drug users recruited from street setti ngs in San Francisco. Of 286 HIV-1 antibody-negative samples, 3 (1.0%) were PCR-positive. Of 49 HIV-1 antibody-positive samples, 1 (2.0%) wa s PCR-negative. Two samples were antibody-indeterminate and PCR-negati ve. This yielded an overall concordance of 331/335 (98.8%), excluding the indeterminate results. These results suggest that current antibody methodology is adequate. However, misclassification among recently in fected individuals may occur, which is of concern in high-incidence gr oups.