Value of confirmation of Chlamydiazyme enzyme immunoassay results in the detection of Chlamydia trachomatis.

The specificity of an EIA (Chlamydiazyme, Abbott) for detection of Chlamydia trachomatis was evaluated by means of a monoclonal antibody blocking reagent (Abbott) and a direct fluorescent antibody test (DFA) (Micro Trak, Syva). Of the 12,864 tested specimens from the urethra and cervix, 666 (5.2%) were positive. When retested with the same technique 625 (4.9%) were again positive. The result in 514 (4.0%) specimens was verified by means of the blocking reagent. Of specimens with absorbance values just below the established cut-off limit (0.07-0.114), 31 of 79 (39.2%) were specifically inhibited, increasing the rate of positive results by 0.25%. The results confirmed with the blocking reagent were in agreement with those obtained by DFA. The findings show that verification of positive Chlamydiazyme results is strongly advisable, in particular in specimens from the cervix.