Serological findings in leprosy. An investigation into the specificity of various serological tests for syphilis.

In serological tests for syphilis, leprosy sera often give biologically false positive reactions. These may be due to the presence of non-specific elements-for example, the ubiquitous lipid antibodies-in the leprosy sera; or they may be the result of errors in technique or unfavourable working conditions in the laboratory. This paper presents the results of an investigation in which several hundred sera from lepers were submitted to four of the so-called "standard" serological tests for syphilis (STS), using either cardiolipin or crude lipid antigens; to a complement-fixation test using as antigen a suspension of Reiter treponemes (PR test); and to the Treponema pallidum immobilization (TPI) test. The investigation was carried out in a moderate climate and in technically well-equipped laboratories.It was found that the number of biologically false positive reactions was not as high as had been expected in the light of previous investigations. It was discovered, moreover, that it was the lipid antigens that were mainly responsible for the non-specific reactions, since both the PR and the TPI test showed a far greater specificity than any of the STS. But the TPI test, though highly specific, is also technically very complicated and therefore not suitable for use in regions where technical facilities are lacking. The authors consider that, in such regions, the simpler PR test will give sufficiently accurate results in the serodiagnosis of treponematoses. It must, however, be recognized that even the treponemal tests are not capable of differentiating between syphilis and yaws infections.