Serological tests for treponemal infection in leprosy patients. An evaluation of the fluorescent treponemal antibody absorption (FTA--ABS) test.

Much has been written about the biological false positive (BFP) reaction demonstrated by reagin tests applied to sera from patients suffering from leprosy. It is well known that a BFP reaction is in all but a very small minority of cases proved or disproved by recourse to specific tests for treponemal infection, i.e. the Treponema pallidum immobilization (TPI) test and/or the fluorescent treponemal antibody absorption (FTA-ABS) test The FTA-ABS test is not as specific as the TPI test and therefore not as well fitted for demonstration of BFP sera as the TPI test (Fribourg-Blanc and Niel, 1967). The TPI test, still the most specific serological test for the diagnosis of treponemal infection (Wilkinson and Rayner, 1966), is largely confined to specialized laboratories because of cost and technical difficulties; by contrast, the FTA-ABS test is less expensive, simpler to perform and all reagents required can be purchased commercially. With care and experience reproducible results can be obtained. For these reasons the FTA-ABS test is likely to become the test of choice for confirmation of BFP reactions in those areas of the world where a laboratory performing the TPI test is not within easy access. This study was undertaken on sera from leprosy patients, to compare the results of the TPI and FTA-ABS tests on those sera which had shown BFP and non-specific reactive results to the more conventional tests for treponemal infection.