A comparison between sorbent and Reiter sonicate in the absorbed fluorescent treponemal antibody test.

Some syphilitic sera still fluoresce with Reiter treponemes as the antigen after treatment with the sorbent used in the FTA-ABS test; this finding indicates incomplete removal of group antitreponemal antibody. Levels of this antibody in normal sera have been studied in relation to the titration of sorbent for use in the test. A comparison has been made of the results of FTA-ABS tests with sorbent and Reiter sonicate and the TPI test on 1141 selected problem sera. Results with the sonicate displayed closer agreement (60.9%) with those of the TPI test than did tests with sorbent 40.8%). The use of sonicate as the sorbing agent is thought to improve the performance of the FTA-ABS test without diminishing its sensitivity.