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P796 Reassessing the gram stain smear (GSS) polymorphonuclear leukocyte (PMN) cutoff for diagnosing non-gonococcal urethritis (NGU)
  1. Gina Leipertz1,
  2. Laura Chambers1,
  3. Sylvan Lowens2,
  4. Jennifer Morgan2,
  5. Sarah Romano1,
  6. Tashina Robinson1,
  7. Lindley Barbee3,
  8. Matthew Golden3,
  9. Lisa Manhart1
  1. 1University of Washington, Epidemiology, Seattle, USA
  2. 2Public Health – Seattle and King County, Seattle, USA
  3. 3University of Washington, Medicine, Seattle, USA


Background Recommended cutoffs for PMNs per high-power field (hpf) to define NGU vary. CDC treatment guidelines specify ≥2 PMNs/hpf. Other guidelines recommend ≥5 PMNs/hpf.

Methods From 08/2014-08/2018, we enrolled symptomatic and asymptomatic male STD clinic patients ≥16 years with exclusively female partners in the past year. Men with gonorrhea or antibiotic use in the past month were excluded. We collected a urethral swab for GSS and urine for Chlamydia trachomatis(CT) and Mycoplasma genitalium (MG) testing (Aptima, Hologic). We calculated Youden’s Index (J=sensitivity+specificity-1), which maximizes sensitivity and specificity, and calculated the proportions of CT/MG cases missed and cases treated in the absence of CT/MG (test-negative) for three PMN/hpf cutoffs. CT/MG co-infections (N=3) were excluded.

Results Among 369 participants, median age was 32 (range 17–71), 53% were white, and 25% were black. Among all men with 0-1, 2-4, 5-9, and ≥10 PMNs/hpf, CT prevalence was 1%, 5%, 11%, and 26%, respectively; MG prevalence was 5%, 3%, 15%, and 17%. J was maximized at ≥5 PMNs/hpf for CT, MG, and CT/MG. Thirteen percent, 17%, and 33% of CT/MG cases were missed at the ≥2, ≥5, and ≥10 PMNs/hpf cutoffs, respectively; 45%, 33%, and 21% of test-negative cases were treated. Among symptomatic men (N=166) with 0-1, 2-4, 5-9, and ≥10 PMNs/hpf, CT prevalence was 0%, 20%, 12%, and 31%, respectively; MG prevalence was 9%, 0%, 18%, and 19%. J was maximized at ≥5 PMNs/hpf for MG, and ≥10 PMNs/hpf for CT and CT/MG. Five percent, 8%, and 25% of CT/MG cases were missed at the ≥2, ≥5, and ≥10 PMNs/hpf cutoffs, respectively; 72%, 64%, and 43% of test-negative cases were treated.

Conclusion The increase in missed CT/MG cases between the ≥2 PMNs/hpf cutoff and ≥5 PMNs/hpf cutoff was minimal; the ≥5 PMNs/hpf cutoff treats fewer cases without CT/MG. The ≥5 PMNs/hpf cutoff appears optimal in this population.

Disclosure No significant relationships.

  • urethritis

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