News: Screening may lead to syphilis overdiagnosis

Due to syphilis testing laboratories reversing the traditional order of screening, there may be overdiagnosis and overtreatment of syphilis, officials from the Centers for Disease Control and Prevention report in the Aug. 15 issue of the Morbidity and Mortality Weekly Report.

CDC officials reviewed data from 116,822 specimens tested for syphilis from four New York City laboratories from Oct. 1, 2005 to Dec. 1, 2006. The laboratories used an automated enzyme immunoassay treponemal screening test (to detect antibodies against Treponema pallidum), followed by a non-treponemal test (rapid plasma reagin) to confirm a positive result. The CDC notes that this is a reversal of the traditional syphilis screening sequence, which has been driven by economics.

The investigators found that 6,587 samples (6%) were initially positive, and of 6,548 of these, 2,884 (44%) were reactive and 3,664 (56%) were non-reactive in subsequent testing. The report suggests that the 3,664 patients would not have been identified by the traditional testing algorithm, and due to a lack of standardized follow-up testing, this may lead to overdiagnosis and overtreatment.

Centers for Disease Control and Prevention (CDC). Syphilis testing algorithms using treponemal tests for initial screening-four laboratories, New York City, 2005–2006. MMWR Morb Mortal Wkly Rep. 2008;57;
872-875.