Comparison of sorbent preparations used in the fluorescent treponemal antibody absorption (FTA-ABS) test.

The physico-chemical and immunological properties of six different sorbent preparations used in the FTA-ABS test were studied. Three of the sorbent preparations contained one heat-stable Reiter treponemal antigen when analysed in immunoelectrophoresis against polyspecific rabbit anti-Reiter Ig and human syphilitic serum. Marked differences were also observed in the osmolarity (1,340-2,434 milliosmol) and protein concentration (6.5-43 mg/ml) of the sorbent products. However, there was no difference in the performance of the six preparations in the FTA-ABS test, suggesting that the effect of sorbent is based on an unspecific inhibition of the reaction between anti-treponemal antibodies and Treponema pallidum.