Following the recent article by Jurado et al1 regarding the prozone reaction in secondary syphilis, we would like to report our experience of the potential problems associated with the use of nontreponemal antibody tests to screen for treponemal infections.
Report of Cases. Case 1.
A 47-year-old man presented with a history of progressive cerebellar signs. There was no history of syphilis. The routine antitreponemal IgG enzyme immunoassay screening test (Captia Syphilis G) showed a positive result with an antibody index of 3.12. Confirmatory testing revealed a negative qualitative VDRL test result, a positive Treponema pallidum hemagglutination assay titer of 10 240, a positive fluorescent treponemal antibody absorbed test result, and a positive antitreponemal IgM enzyme immunoassay (Captia Syphilis M) with an antibody index of 1.2. Repeated VDRL testing, using diluted serum samples, gave a titer of 64, suggesting that the initial false-negative result was attributable to the prozone phenomenon