The CSF‐FTA test and the significance of blood contamination

Although the fluorescent treponemal antibody absorption (FTA-ABS) test has found wide application in the diagnosis of syphilis, the cerebrospinal fluid fluorescent treponemal antibody (CSF-FTA) test is still controversial in the diagnosis of neurosyphilis. We found the CSF-FTA test extremely sensitive to contamination with FTA-ABS-reactive blood at concentrations in CSF that could not be detected by visual inspection. Interpretation of a reactive test should be made with caution if red cells are present in CSF.