Rapid diagnosis of Chlamydia trachomatis in male patients by antigen detection in urine samples

To investigate the diagnostic value of testing urine samples as a rapid method for the detection of chlamydial antigen in males, first-catch urine (FCU) and urethral swab samples were obtained from 668 male patients and examined by an enzyme immunosorbent assay (EIA). Positive results were further analyzed by direct fluorescence antibody tests of the EIA sediment. Antigen detection was possible in 12.7% out of the urethra, in 10.8% out of FCU and in a total of 14.5% of the tested persons. Testing only FCU would have missed chlamydia detection in 25 (25.8%) out of a total of 97 chlamydia-positive males. Testing only genital samples would have missed 12 positive cases (12.4%). The sensitivity and specificity of the EIA test of FCU as compared with urethral swabs were 70.6 and 97.9%, respectively, and differed between urine collected before (sensitivity: 84%; specificity: 98.6%) and after (sensitivity: 65%; specificity: 97.7%; p = 0.1254) urethral sampling. The quantitative evaluation of the EIA results demonstrates that the mean value of the extinction rates was highest in specimens corresponding to a positive result from both sampling sites. This study indicates that the chlamydial detection rate was lower in FCU than in urethral samples. FCU testing may be suitable when urethral sampling is not possible; due to its high rate of unconfirmed borderline extinction, positive results should be confirmed with another chlamydial antigen detection test such as direct immunofluorescence.