Development of an Enzyme-Linked Immunosorbent Assay (ELISA) for the Detection of Nontreponemal Anti-Cardiolipin Antibodies in the Sera of Patients with Syphilis

Background: We describe an enzyme-linked immunosorbent assay (ELISA) for the detection of nontreponemal antibodies. This assay is ideal for the automation of high throughput screening of sera from patients with syphilis.

Methods: The nontreponemal (cardiolipin) antigen was chemically modified, and was attached covalently to amine functionalized micro titer plates.

Results: One hundred fifteen reactive serum samples with known stages of syphilis and 194 nonreactive for a total of 309 samples were evaluated and the results compared to the predicate rapid plasma reagin (RPR) test.  Also, 182 samples from diseases other than syphilis were included in this study.  The sensitivity of the EIA was 99.1%, and the specificity was 95.3%.

Conclusions: These results indicate that the nontreponemal EIA test can be used for the screening of a large volume of samples using the traditional syphilis testing algorithm of screening with a nontreponemal test and confirming the results with a treponemal test.