[Specific IgM tests in syphilis diagnosis]

A total of 359 sera of untreated patients with syphilis were examined by three methods for the detection of Treponema pallidum specific IgM antibodies, the 19S-IgM-FTA-ABS test, the IgM solid phase haemadsorption assay (IgM-SPHA), and the IgM Captia assay. The results were compared and evaluated. In primary syphilis, the 19S-IgM-FTA-ABS and IgM-captia yielded reactive results in all patients, whereas only 40% were positive in the IgM-SPHA; the corresponding values for early latent syphilis wee 96.0%, 89.8% and 73.1%, respectively. In secondary syphilis, the reactivity of one serum out of 27 was missed by IgM captia and that of another, by the IgM-SPHA. Mean values (ELISA units = extinction/cut-off) of IgM-captia were higher in primary (2.25) than in secondary syphilis (1.70). In neurosyphilis, only the IgM-SPHA test detected reactivity in all sera, sensitivity for 19S-IgM FTA-ABS and IgM-Captia was 50.0% and 23.1%, respectively. Specificity of the IgM-Captia test results, determined in 386 sera, was 91.2%. The results of specific IgM tests are essential in the diagnosis of congenital syphilis as well as in the recognition of reinfection; they indicate the need for treatment and are useful in the assessment of the effectiveness of therapy.