Profile of sexually transmitted infections causing urethritis and a related inflammatory reaction in urine among heterosexual males: A flow-cytometry study

BACKGROUND: Information about the use of flow cytometry in the diagnosis of male urethritis is scarce. The current study aims to evaluate the performance of flow cytometry on first-voided urine in males with infectious urethritis (Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium and Trichomonas vaginalis). METHODS: Male patients of the Andrology Centre (Tartu University Hospital, Estonia) were recruited during the period March 2015 –January 2018. Cases included 306 patients with infectious urethritis caused by Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma genitalium and/or Trichomonas vaginalis. The control group consisted of 192 patients without uro-genital complaints, negative tests for C. trachomatis, N. gonorrhoeae, M. genitalium and T. vaginalis from first-voided urine and no inflammation in first-voided urine, mid-stream urine and urine after prostate massage. C. trachomatis, N. gonorrhoeae, M. genitalium and T. vaginalis were detected from first-voided urine using polymerase chain reaction (PCR) method. First-voided urine was analysed using urine particle analyzer Sysmex UF-500i. RESULTS: The most prevalent infection was chlamydia (64.1%), followed by Mycoplasma genitalium (20.9%), gonorrhoea (7.8%) and trichomoniasis (1.6%). Gonorrhoea caused the highest flow-cytometric leucocyte/bacteria count, followed by chlamydia and Mycoplasma genitalium. Trichomonas vaginalis showed nearly absent inflammation in first-voided urine. Using an empiric flow-cytometry diagnostic threshold for urethritis in first-voided urine (leucocytes ≥ 15/μl and bacteria ≥ 20/μl) the total calculated sensitivity was over 90%. However, when applying such criteria for deciding whether to perform first-voided urine PCR for C. trachomatis, N. gonorrhoeae, M. genitalium and T. vaginalis or not, we could miss 23 cases with infectious urethritis that makes up 7,5% of all proven cases. CONCLUSIONS: Flow cytometry of first-voided urine can be considered as a rapid and objective screening method in case of suspected male infectious urethritis.