Problems affecting performance of the fluorescent treponemal antibody-absorption test for syphilis

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Abstract
Immunofluorescent staining of Treponema pallidum was studied to clarify the effect of 3 factors on the results of the fluorescent treponemal antibody-absorption test: heat inactivation of sera [human] at 56.degree. C for 30 min before testing, use of multicircle slides and W illumination to visualize and assess unstained treponemes on reactive and nonreactive smears. Serum inactivation before testing was not necessary for detection of immunoglobin (Ig) G antibody, but an IgM prozone was detected in unheated serum. On multicircle slides, a false-positive reaction could be obtained in 30 s at 37 and 25.degree. C if a smear where a nonreactive serum had been placed was crossed by a strongly reactive serum from another circle. W illumination proved necessary for correct assessment of unstained treponemes on all fluorescent treponemal antibody-absorption test smears, reactive or nonreactive. The possible role of these factors in incorrect fluorescent treponemal antibody-absorption test results is discussed.