Chlamydia Trachomatis Infection in a High-risk Population: Comparison of Polymerase Chain Reaction and Cell Culture for Diagnosis and Follow-up

A study to compare the polymerase chain reaction (PCR) test with the cell culture method in diagnosing urogenital Chlamydia trachomatis infections was performed. From 497 patients (212 women, 285 men) attending an outpatient clinic for sexually transmitted diseases, a total of 814 samples (female patients, cervix and urethra; male patients, urethra) were collected. This total included follow-up samples from 35 women and 35 men positive for C. trachomatis by cell culture and/or PCR test, which were collected 2 weeks after treatment with doxycycline (two 100-mg doses per day for 7 days). The PCR test was performed directly on clinical samples without performing phenol-chloroform extraction and ethanol precipitation of DNA. The prevalence of C. trachomatis as measured by positive cell culture was 64 of 497 (12.9%) for all patients, 31 of 212 (14.6%) for women, and 33 of 285 (11.6%) for men. The prevalences as measured by positive PCR test were 71 of 497 (14.3%), 36 of 212 (17.0%), and 35 of 285 (12.3%), respectively. The sensitivities of the cell culture and the PCR test compared with that of true-positive samples were 77.5 to 78.4% and 99.0 to 100.0%, respectively. Discrepancies between cell culture and the PCR test were found for 23 of 497 patients (4.9%), 19 of 212 females (9.0%), and 4 of 285 males (1.4%). Nineteen pretreatment samples from 19 patients (4 female endocervical, 13 female urethral, and 2 male urethral samples) were cell culture negative and PCR test positive, while 1 pretreatment female endocervical sample was cell culture positive and PCR test negative. The posttreatment samples from all patients were cell culture negative, but the PCR test remained positive for 3 of 70 patients (1 female endocervical and 2 male urethral samples). One of these samples became spontaneously negative in three more weeks. The medical history of the individual patient and the negative PCR tests after treatment for nearly all patients support our hypothesis that the positive PCR test results were clinically relevant for the cell culture-negative but PCR test-positive but PCR test-positive patients of the population studied.