Comparison of reticulate and elementary body antigens in detection of antibodies against Chlamydia trachomatis by an enzyme-linked immunosorbent assay.

Reticulate bodies from a type C and elementary bodies from a type L2 strain of Chlamydia trachomatis were isolated and used as antigens in an enzyme-linked immunosorbent assay (ELISA). Results obtained for human sera with these two antigens used in the ELISA were compared with each other and with results obtained for the same sera by the micro-immunofluorescence test. Negative control populations included cloistered nuns and children with respiratory infections. Populations at risk for chlamydial infection consisted of 42 men with nongonococcal urethritis attending a sexually transmitted diseases clinic and 42 college women who had contact with men with nongonococcal urethritis. ELISAs done with the two antigens were equivalent to each other and to the micro-immunofluorescence test in the ability to predict the presence or absence of infection. None of the tests had high predictive values for the men with urethritis. However, the negative predictive value of both the micro-immunofluorescence test and the elementary body ELISA was 0.92 for the college women. Such serological tests may be of value in screening selected populations for subclinical infections with C. trachomatis.