Impact of urine collection order on the ability of assays to identify Chlamydia trachomatis infections in men

Background: Noninvasive urine samples have been used to diagnose Chlamydia trachomatis infections, with the assumption that the first-void urine (FVU), defined as the first 20 to 30 ml at any micturition, would be the optimal collection. We compared testing technologies on first, second, and third volumes for diagnosis. Goal. The goal was to test in nonculture assays three sequential volumes of urine from men also undergoing urethral swabbing for C trachomatis culture specimens. Study Design: A total of 237 men attending an STD clinic (C trachomatis prevalence, 11%) collected three containers of urine (each containing 20-30 mL) for testing in four nonculture assays. A urethral swab specimen was tested in cell culture. Results: The numbers of men positive by testing of FVU with nucleic acid amplification (LCx chlamydia), nucleic acid hybridization (PACE 2), enzyme immunoassay (Chiamydiazyme), and a leukocyte esterase dipstick were 26, 7, 14, and 11, respectively; urethral culture identified 6 of the infected men. Comparative testing of all voids from the 26 men positive by the FVU assays demonstrated a reduction of LCx-positives. Non-amplified-test positivity declined precipitously in subsequent voids, approaching zero in the third void. The presence of symptoms and time of last void up to 8 hours had little effect on the number of positives detected by LCx of FVU. Conclusion: Amplified testing of FVU was most effective for diagnosing infection in these men.