New developments in ELISA verification of anti-HIV screening of blood donors.

First generation ELISA screening assays for antibodies to HTLV-III (HIV) generated between 0.1 and 1.0% false positive results. Western blot analysis in specialized reference centers is almost uniformly used as a method to confirm the specificity of the ELISA results. Yet, the high cost, time delay and lack of standardization in these systems cause a growing demand for tests that can be performed on site and that can at least reduce the number of sera that have to be sent to reference centers. Such tests thus should primarily be aimed at the detection of false positive results. Ancillary to the Vironostika anti-HTLV-III screening test, we developed a set of reagents (VERIFY) which can be used for the verification of initially or repeatedly positive screening results. The test employs a reagent specifically blocking true HTLV-III-anti HTLV-III reactions, a reagent blocking HLA-anti HLA reactions and a control reagent. Use of this test may reduce the number of sera found false positive by reference methods by more than 90%. The introduction of improved versions and second generation screening assays obviously will reduce the number of false positive results. Yet the significant results of this verification assay and the ease with which it can be integrated in the screening procedures will make it a valuable tool in the blood bank screening program.