Comparison of Traditional and Reverse Syphilis Screening Algorithms in Medical Health Checkups

BACKGROUND: The syphilis diagnostic algorithms applied in different countries vary significantly depending on the local syphilis epidemiology and other considerations, including the expected workload, the need for automation in the laboratory and budget factors. This study was performed to investigate the efficacy of traditional and reverse syphilis diagnostic algorithms during general health checkups. METHODS: In total, 1,000 blood specimens were obtained from 908 men and 92 women during their regular health checkups. Traditional screening and reverse screening were applied to the same specimens using automatic rapid plasma regain (RPR) and Treponema pallidum latex agglutination (TPLA) tests, respectively. Specimens that were reverse algorithm (TPLA) reactive, were subjected to a second treponemal test performed by using the chemiluminescent microparticle immunoassay (CMIA). RESULTS: Of the 1,000 specimens tested, 68 (6.8%) were reactive by reverse screening (TPLA) compared with 11 (1.1%) by traditional screening (RPR). The traditional algorithm failed to detect 48 specimens [TPLA(+)/RPR(−)/CMIA(+)]. The median TPLA cutoff index (COI) was higher in CMIA-reactive cases than in CMIA-nonreactive cases (90.5 vs 12.5 U). CONCLUSIONS: The reverse screening algorithm could detect the subjects with possible latent syphilis who were not detected by the traditional algorithm. Those individuals could be provided with opportunities for evaluating syphilis during their health checkups. The COI values of the initial TPLA test may be helpful in excluding false-positive TPLA test results in the reverse algorithm.

Evaluation of AutoLab Rapid Plasma Reagin and AutoLab Treponema pallidum Latex Agglutination for Syphilis Infection Testing / 임상검사와정도관리

BACKGROUND: Automated assays have recently been developed for efficient serological testing of syphilis infection. Here, we evaluate the performance of new automated serological assays for syphilis infection. METHODS: The precision, linearity, and detection limit of the automated kits AutoLab rapid plasma reagin (RPR) (IVD-RPR) and AutoLab (Treponema pallidum Latex Agglutination) TPLA (IVD-TPLA) (IVDLab Co., Korea) were evaluated using an immunoturbidimetric method. In addition, the results of these tests were compared with those obtained using the HiSens Auto RPR LTIA (HBi-RPR) and HiSens Auto TP LTIA (HBi-TPLA) tests (HBi Co., Korea) with 122 serum samples. RESULTS: Both the IVD-RPR and IVD-TPLA kits showed acceptable precision for the positive controls (IVDLab Co., Korea). The within-run and total precision of IVD-RPR were better than those of HBi-RPR at cut-off levels (CV, 7.0% to 7.4% for IVD-RPR; CV, 33.3% to 40.0% for HBi-RPR). The IVD-RPR and IVD-TPLA kits demonstrated acceptable linearity and limits of detection. The agreement rate between IVD-RPR and HBi-RPR was 83.60% (102/122). Nineteen samples were IVD-RPR negative but HBi-RPR positive; 12 of these were from patients with a history of syphilis. The agreement rate between IVD-TPLA and HBi-TPLA was 96.72% (118/122). All discrepant results were IVD-TPLA positive and HBi-TPLA negative. CONCLUSIONS: IVD-RPR and IVD-TPLA exhibited acceptable precision, linearity, and limits of detection for the diagnosis of syphilis infection. IVD-RPR was suitable for monitoring syphilis infections with good precision that was near cut-off levels. IVD-TPLA was useful for detecting primary syphilis infection.