Blinded proficiency testing of FTA-ABS test.

In 1976 and 1977, 28 state laboratories participated in a blinded proficiency testing study of syphilis serologic tests. The test considered of a battery of 50 duplicate reagin-positive sera; 12 specimens were obtained from syphilitic patients. The median reproducibility scores for the VDRL and FTA-ABS tests were the same, 92%, and the scores for the two tests were correlated. Given the relatively low prevalence of untreated syphilis in the United States today, serologic results that are highly predictive of syphilis are obtainable only from the most proficient laboratories, if unselected sera are tested. Reactivity in the VDRL and FTA-ABS tests does not prove the diagnosis of syphilis. Physicians must use clinical judgment to preselect patients for serologic testing.