Comparison of two immunofluorescence tests for detecting antibodies to C. trachomatis

Two immunofluorescence tests were compared for detecting antibodies to chlamydiae. The inclusion antigen test was more sensitive, detecting antibodies in more sera and at higher titres. The micro-IF test was more specific, differentiating between antibodies to C. trachomatis and those to C.IOL 207. Antibodies to this non-genital chlamydial type accounted for half the positive results. These antibodies can cause the prevalence of C. trachomatis infections to be over estimated when genus-specific serology tests are used.