WHAT IS THE FLUORESCENT TREPONEMAL ANTIBODY–ABSORBED DOUBLE-STAIN (FTA-ABS DS) TEST?
Syphilis is a complex, sexually transmitted disease characterised by a wide range of symptoms that imitate other diseases and is caused by the organism Treponema pallidum. This test provides the most sensitive detection of treponemal antibodies for syphilis in all stages. It differentiates biologic false-positive results from true syphilis-positive results and can help diagnose syphilis when definite clinical signs are present, but other tests are negative. This test is positive in the treponemal diseases of bejel, pinta, syphilis, and yaws. Before testing, the serum is treated to remove antibodies that could cause false-positive results. The technique involves using fluorescence microscopy with special filters that decrease the amount of natural fluorescence from the background of the specimen. Fluorescein-conjugated antibodies to IgG are added as a counterstain to the stained specimen, and the treponemes are identified as they fluoresce in combination with the antibodies.