Diagnostic dilemma of the single screening test used in the diagnosis of syphilis in Nepal.

Syphilis screening by the nontreponemal rapid plasma reagin (RPR) test is not usually followed up by specific treponemal tests in most of the resource poor healthcare settings of Nepal. We analyzed serum specimens of 504 suspected syphilis cases at the immunology department of the national reference laboratory in Nepal during 2007-2009 using RPR test and Treponema pallidum hemagglutination assay (TPHA). In overall, 35.7% were positive by both methods (combination) while 13.1% were RPR positive and TPHA negative, 8.7% were positive by TPHA only and 42.5% were negative by both methods. Among the RPR reactive (n = 246), 73.2% were positive by TPHA. Non-specific agglutination in RPR testing was relatively higher (26.8%) compared to TPHA (19.6%). Although TPHA was found more specific than RPR test, either of the single tests produced inaccurate diagnosis. Since the single RPR testing for syphilis may yield false positive results, specific treponemal test should be routinely used as confirmatory test to rule out false RPR positive cases. More attention needs to be paid on formulation of strict policy on the implementation of the existing guidelines throughout the country to prevent misdiagnosis in syphilis with the use of single RPR test.