EVALUATION OF AUTOMATED SYPHILIS SCREENING FOR BLOOD DONORS USING TREPONEMA PALLLIDUM PARTICLE AGGLUTINATION (TPPA) TEST

Abstract

Sera obtained from six patients with recently infected syphilis showed positive reaction by Treponema pallidum Particle Agglutination (TPPA, Fujrebio), a newly developed test for syphilis infection. The results were confirmed by other immunoassays such as enzyme immunoassay (Imzyn M-TP, Fujirebio) and/or immunofluorescence (FTA-ABS, Nihon Touketukansou). In contrast, they were negative by Serodia-TP (Fujirebio). In a seroconversion panel, TPPA showed positive reaction earlier than conventional RPR (rapid plasma reagin, Kaketuken). IgM fractions prepared from five recently infected patients were all positive by TPPA, while only one was positive by Serodia-TP. These results indicate that TPPA is able to detect anti-TP in the early phase of infection. In the next step, we evaluated the application of this test for blood donor screening with a PK7200 automated pretransfusion analyzer for agglutination assays (Olympus). After establishing optinal conditions for TPPA in the PK7200 (PK-TPPA), 4,902 samples were simultaneously tested by manual and automated testing. Positive samples were manually retest ed. There was no false negative results by the PK test, while both the manual PK tests yielded a similar rate of false positive results. In a simultaneous test with PK-TPPA and RPR, respec tively 43 and 65 of 14,106 donor samples were repeatedly positive. Of 21 samples showing positive reaction in both tests, 17 were confirmed as IgG type anti-TP by FTA-ABS. Of 20 PK-TPPA(+)RPR(-) samples, 7 were IgG type anti-TP positive. None of the 44 RPR(+)-TPPA(-) samples were positive by FTA-ABS. We conclude that the PK-TPPA is sensitive enough to detect IgM type anti-TP and acceptable for donor screening.