ANTIBODIES OF CHLAMYDIA SPECIES IN PATIENTS ATTENDING A GENITOURINARYCLINIC AND THE IMPACT OF ANTIBODIES TO C-PNEUMONIAE AND C-PSITTACI ONTHE SENSITIVITY AND THE SPECIFICITY OF C-TRACHOMATIS SEROLOGY TESTS

In a retrospective study, the prevalence of antibodies to Chlamydia tr achomatis serovars D to K, C. pneumoniae, and C. psittaci in cases att ending a genitourinary, clinic was examined. Blood samples were collec ted from 7,002 cases attending the clinic in Doncaster, England betwee n May 1983 and May 1990. Sera from these samples were tested by a modi fied microimmunofluorescence test using panels of microdots of egg-gro wn, purified elementary bodies representing a pool of C. trachomatis D to K, a single C. pneumoniae agent, a single C. psittaci agent, and a negative control. Serum specimens were tested for the presence of IgG and IgM at starting dilutions of 1/16 and 1/8, respectively. Chlamydi al IgG at a level of 1/16 or higher and IgM at a level of 1/8 or highe r was present in 66.6% and 2.6% of samples, respectively. Species-spec ific or cross-reactive IgG against C. trachomatis D to K, C. pneumonia e, and C. psittaci was present in 32.6%, 25.1%, and 0.1% of the sample s, respectively. In 8.7% of samples, the level of IgG was similar agai nst two or all three species (group-specific). IgM against C. trachoma tis D to K, C. pneumoniae, or C. psittaci was present in 2.5%, 0.03%, and 0.04% of the samples, respectively. The results of the study show that antibodies to C. pneumoniae and C. psittaci account for up to hal f of all chlamydia IgG positive cases attending genitourinary clinics. We therefore recommend that a serologic test that can differentiate a ntibodies to C. trachomatis from those to C. pneumoniae and C. psittac i, such as the modified microimmunofluorescence test, should be used f or screening and for presumptive serodiagnosis of genital infections.