Congenital syphilis: the diagnostic value of the rheumatoid factor in symptomatic patients

The rheumatoid factor (RF) latex test was used as a side-room investigation for congenital syphilis. Thirty-four infants aged 0-4 months with suggestive clinical signs and unknown serological tests for syphilis were studied. Nineteen were subsequently diagnosed as having congenital syphilis on the basis of positive serology, while 15 infants had other conditions. The sensitivity of the RF latex test was 95% with a specificity of 80%. Reactive tests were seen only in neonates with congenital infections (p < 0.001). The total IgM test had a similar sensitivity in the diagnosis of congenital syphilis but its specificity (14%) was significantly less (p < 0.001). In areas where the prevalence of congenital syphilis is high, the RF latex test is useful for rapid diagnosis of the condition while confirmatory tests are awaited.