Roche Diagnostics Solutions Pleasanton, California, United States
Background/Case Studies: Syphilis is caused by the spirochete, Treponema pallidum (TP). Although rare, it can be transmitted through blood transfusion and requires testing in all blood donations. Treponemal assays for the detection of antibodies to Treponemal specific antigens are in common use for screening blood donations on high throughput automated instruments.
A study was performed to evaluate the sensitivity and specificity of Elecsys Syphilis, Beckman Coulter PK® TP System (PK-TP) and Newmarket Biomedical PK7400 TP HA REAGENT (PK-TP-HA) assays.
Study
Design/Methods: Elecsys Syphilis is an electrochemiluminescent immunoassay (ECLIA) for the detection of total antibodies (IgG and IgM) to TP in human serum and plasma, including volunteer donors of whole blood and blood components. The assay is used with the Cobas® Pro serology solution, equipped with the Cobas e 801 automated analytical unit, and is available in the US. The PK-TP and PK-TP-HA assays detect total antibodies based on the principle of agglutination and pattern recognition using the PK7300 and PK7400, respectively.
Evaluation of specificity for Elecsys Syphilis and PK-TP on the PK7300 System included 4556 routine blood donor samples (2052 serum, 2504 plasma). All initial reactives were tested in duplicate. Samples reactive by one or both assays were further tested by CAPTIA™ Syphilis-G EIA and Zeus IFA FTA-ABS Test, with follow-up testing if the status remained inconclusive.
Sensitivity of Elecsys Syphilis and PK-TP-HA on the PK7400 System was assessed using 552 positive samples: 76 primary infection, 64 secondary infection, 97 latent infection, and 315 uncharacterized. Discordant samples were tested with the Abbott™ ARCHITECT™ Syphilis TP assay.
Results/Findings: Four of 4556 donations were reactive in both syphilis-screening assays and were confirmed positive. Nineteen of 4552 samples had discrepant results and all were determined to be negative based on supplemental or follow-up testing. Specificity in the 4552 samples was 99.91% (CI: 99.77, 99.97; 4548/4552) for Elecsys Syphilis, and 99.67% (CI: 99.46, 99.80; 4537/4552) for PK-TP.
16/552 positive samples were nonreactive on PK-TP-HA, for a sensitivity of 97.10 (CI: 95.34,98.21) vs 100% (CI: 99.31, 100.00) for Elecsys Syphilis. Conclusions: Elecsys Syphilis demonstrated high sensitivity and specificity compared to the PK-TP and PK-TP-HA assays.
