Syphilis.

The clinical manifestations of syphilis can resemble many diseases. The diagnosis can be confirmed through serologic tests and by direct microscopic observation of Treponema pallidum, subspecies pallidum in lesion, biopsy, or autopsy specimens. Direct microscopic examination may be carried out by darkfield methods or by immunofluorescent staining. The serologic testing sequence is usually a screening nontreponemal test followed by confirmation with a specific treponemal test. Serologic tests for syphilis have been highly standardized in the past, but today quality control lies in the hands of the laboratorian.