A sonicate of Reiter treponemes used as sorbing agent in the fluorescent treponemal antibody-absorption (FTA-ABS) test.

A sonicate of Treponema phagedenis biotype Reiter (Reiter treponemes) was used as sorbing agent in parallel with sorbent in the FTA-ABS test. By diluting the Reiter treponemal antigens in approximately 0.5 M NaCl, the Reiter sonicate could be produced in sufficient quantities for its use in routine FTA-ABS. In crossed immunoelectrophoresis against a rabbit anti-Reiter immunoglobulin, 40 Reiter antigens were detectable in the sonicate and only one in the sorbent. The diluted sonicate and the sorbent had similar osmolarity and almost similar pH. FTA-ABS with sonicate and sorbent had similar sensitivity in untreated early and late syphilis. Only in treated early syphilis was non-reactivity usually obtained somewhat earlier with sonicate than with sorbent. Both FTA-ABS with sonicate and sorbent had a specificity near 98%. It is concluded that replacement of sorbent with sonicate in the routine FTA-ABS test would increase the costs without substantial improvements of the test.