Background: Nongonococcal urethritis (NGU) is common, yet up to 50% of cases have no defined etiology. The extent to which risk profiles and clinical presentations of pathogen-associated and idiopathic cases differ is largely unknown.
Methods: Urethral swabs and urine specimens were collected from 370 NGU treatment trial participants who sought care at a sexually transmitted disease clinic in Seattle, WA from 2007 to 2009 and had a visible urethral discharge and/or microscopic evidence of urethral inflammation assessed by Gram-stain (≥5 polymorphonuclear leukocytes per high-powered field [PMNs/HPF]). Neisseria gonorrhoeae, Chlamydia trachomatis (CT), Mycoplasma genitalium (MG), Trichomonas vaginalis (TV), and Ureaplasma urealyticum (UU) were detected in urine, using nucleic acid amplification tests. Cases negative for all assessed pathogens were considered idiopathic. Bivariate and multivariate analyses identified clinical, sociodemographic, and behavioral factors associated with detection of specific pathogens.
Results: After excluding 3 participants with gonococcal infection, pathogens were detected in only 50.7% of the 367 eligible cases: CT in 22.3%, MG in 12.5%, TV in 2.5%, and UU in 24.0%, with multiple pathogens detected in 9.5%. In all, 3.5% of cases were negative for CT, MG, and TV but lacked speciated ureaplasma results. The remaining cases (45.8%) were considered idiopathic. Pathogen detection was associated with young age, black race, risky sexual behaviors, cloudy or purulent discharge, and visible discharge plus≥5 PMNs/HPF. In contrast, idiopathic cases were more likely to report prior NGU, were older and less likely to be black, or have an abnormal urethral discharge on examination, compared to all other cases. These cases were not associated with any high risk behaviors.
Conclusions: NGU is a heterogeneous condition. Pathogen detection was associated with a variety of traditional risk factors and clinical features; whereas, idiopathic cases tended to be diagnosed among lower-risk men.