Syphilis testing - mucocutaneous ulcer
Last updated: Wednesday, 12, September, 2007
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Wet preparation from base of lesion (eg, chancre) after gentle cleansing with saline.
The slide must be examined immediately by darkfield microscopy.
If this is not available on site, a smear on a glass microscope slide should be submitted for IFA or DFA testing.
A swab may be collected if PCR testing is available.
Darkfield microscopy; DFA or IFA on fixed smear; nucleic acid detection (PCR testing) on swab after amplification.
Diagnosis of primary syphilis.
Treponema pallidum is identified by characteristic morphology and motility on darkfield microscopy.
Because it is difficult to distinguish T. pallidum from other spirochaetes which are part of the normal flora of the gastrointestinal tract, darkfield microscopy is unsuitable for the examination of specimens from oral or anal lesions.
A positive result (darkfield microscopy, IFA or DFA) confirms a clinical diagnosis of primary syphilis. A negative result does not exclude the diagnosis.
PCR testing is under evaluation in some laboratories. A positive result is suggestive of current infection with Treponema pallidum. A negative result soes not exclude the diagnosis.
Kellog DS. Health Lab Sci 1970; 7: 34-41.
Garner MF and Robson JH. J Clin Micro 1968; 21: 576-577.