Problems with beaded fluorescence pattern in FTA-ABS test

The significance of false-positive FTA-ABS fluorescence in connective tissue diseases and other clinical conditions was evaluated by studying the serum from several groups of patients. In 12% of 67 patients without syphilis, serum with an antinuclear antibody (ANA) titer of 1:32 or greater gave low intensity FTA-ABS test fluorescence. In 20% of 150, patients (2.7% with a history of syphilis), serum with rheumatoid factor (RF) titers of 1:640 or greater demonstrated some reactivity. Only 1.3% of 75 donors of normal blood showed low-grade FTA-ABS fluorescence. In 385 patients with diagnostic problems, 2.1% of the serum demonstrated the beaded pattern. Patterns varied, depending on the treponemal antigen preparation and the duration of serum storage. Also, multiple specimens from the same patient produced different patterns. Furthermore, the beaded pattern could be demonstrated in patients with a history of syphilis, with other medical disorders, and in apparently normal persons.