Sensitivity of 20-minute voiding intervals in men testing for Chlamydia trachomatis

Men are recommended to not urinate for at least 1 hour before urine testing for Chlamydia trachomatis, but some studies have shown that recent urination does not impact test sensitivity for nucleic acid amplification tests. The objective of this study was to estimate the sensitivity of chlamydia testing using samples obtained 20-minutes post void.

We recruited men returning to Sydney Sexual Health Centre for treatment of urethral Chlamydia trachomatis infection between July 2009 and February 2011. A short questionnaire was used to elicit symptoms, and 2 first-void urine samples were collected-the first after the standard 1 hour minimum and the second 20 minutes later. Men with clinical or microbiologic evidence of urethritis, men receiving antibiotic treatment, and those who had urinated within the last hour were excluded. Samples were tested using Roche COBAS Amplicor PCR. The proportion of samples testing positive at 20 minutes post void was determined using the 1-hour post void sample as a gold standard.

Thirty-one men with confirmed chlamydia infection were included in the analysis. Of these, 29 of 31 (93.5%) were positive at 20 minutes (95% CI: 78.6%-99.2%).

The sensitivity of 20-minute voiding intervals in asymptomatic men remains reasonably high relative to standard voiding intervals. Removing the barrier of a 1-hour voiding interval should be considered during opportunistic screening.