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October 1966


Author Affiliations

Division of Dermatology Department of Medicine University of California San Francisco Medical Center

Arch Dermatol. 1966;94(4):527. doi:10.1001/archderm.1966.01600280145026

To the Editor.—  Carr et al1 suggest an increase in false-positive serologic tests for syphilis in elderly men. A study of certain clinical and laboratory variables revealed no significant differences between individuals with false-positive reactions and patients with latent syphilis.A battery of three nontreponemal tests was performed on sera from each of about 10,000 individuals, and a reactive test was obtained in 269. The Treponema pallidum immobilization (TPI) test was used to distinguish latent syphilis from false-positive reactions, and 162 false-positive reactors were found.Screening tests for syphilis are carefully standardized; however, none has demonstrated absolute sensitivity, and the specificity is approximately 99.5% to 99.9%. Thus in testing 10,000 sera, a single test would give 10 to 50 reactive tests due to physicochemical factors or day-to-day variability in testing. The use of three screening tests magnifies this variable, which we consider a technical aspect of the test procedure

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