[HIV (HTLV III/LAV) serology: experiences based on more than 42,000 tests]

1,032 sera of diverse origin (AIDS risk groups, prostitutes, inpatients, blood donors) exhibiting a positive HIV (HTLV III/LAV) ELISA result (Organon and/or Abbott) were investigated with different HIV confirmation assays (Western blot, WB; immunofluorescence, IF; competitive enzyme immunoassay against cloned gp41- and p24-antigen). Sera were finally evaluated as positive if at least two confirmation assays turned out positive (IF and WB; IF and p24, gp41; WB and p24, gp41; IF and WB and p24, gp41). Test results were considered false if the respective finding (IF or WB or p24, gp41) differed from two other confirmatory assays. 1,001 out of 1,032 sera (97%) yielded corresponding results in IF and WB. The remaining 3% of the investigated sera showed false positive, false negative, non-interpretable IF results and non-interpretable WB findings. The present study demonstrates that a positive HIV test should be confirmed by at least two confirmatory tests, one of which should be the WB. Non-corresponding results in confirmatory tests necessitate a third test system.