Evaluation of a Rapid Immunochromatographic Treponemal Antibody Test Comparing the Treponema Pallidum Particle Agglutination Assay

Background: In addition to conventional tests, several methods for detection of treponema-specific antibodies in clinical settings have been recently introduced. We aim to comparatively evaluate a rapid immunochromatographic test (ICT) for Treponema pallidum specific antibody (SD Bioline Syphilis 3.0) and the T. pallidum particle agglutination (TPPA) assay.

Methods: In all, 132 serum samples from 78 syphilis patients and 54 syphilis-negative controls were analyzed. SD Bioline Syphilis 3.0 test (Standard Diagnostic, Inc., Yongin, Korea) was evaluated and compared to Serodia TPPA assay (Fujirebio, Inc., Tokyo, Japan). All discrepant results between the two assays were repeatedly tested and evaluated by the fluorescent treponemal antibody-absorption (FTA-ABS) assay. Test reproducibility and 95% limit of detection of SD Bioline Syphilis 3.0 were determined across three different lots for seven consecutive days in triplicate. Interference due to autoantibodies and pregnancy was also tested.

Results: Percent agreement between SD Bioline Syphilis 3.0 and TPPA assays was 99.2%. Sensitivity and specificity were 100%, respectively. In TPPA assay, test-to-test, day-to-day, and lot-to-lot variations were not identified until 1:320 titer (eightfold dilutions). There was no interference due to the presence of antinuclear antibodies or samples or pregnancy.

Conclusions: Percent agreement of SD Syphilis 3.0 and TPPA was very good. Sensitivity and specificity were appropriate for T. pallidum antibody detection. Thus, a rapid ICT could be suitable for syphilis antibody detection.