Microscopy of Gram-stained urethral smear in the diagnosis of urethritis: Which threshold value should be selected?

The aim of this study was to investigate the sensitivity of GSS in the diagnosis of urethritis in patients who present to the outpatient clinic with symptoms of urethritis. Sixty-three male patients who presented to our outpatient clinic with symptoms of urethritis between January and March 2018 were evaluated. Urethral smear samples obtained from patients were evaluated both by GSS examination and by Real-time Multiplex Polymerase Chain Reaction (rt-MPCR) assay. The sensitivity and specificity of GSS in detecting gonococcal urethritis (GU) and nongonococcal urethritis (NGU) were calculated for threshold values of ≥5 and ≥2 PMNL/HPF. The mean age was 33.2 ± 7.1 years. According to the rt-MPCR results, 14 patients had GU and 27 patients had NGU. A threshold value of ≥5 PMNL/HPF in the GSS demonstrated 92.9% sensitivity in the diagnosis of GU and 55.6% sensitivity in the diagnosis of NGU. A threshold value of ≥2 PMNL/HPF reached 100% sensitivity for GU and 92.6% sensitivity for NGU. A cut-off value of ≥5 PMNL/HPF in the GSS has low sensitivity in the diagnosis of NGU. On the other hand, a threshold value of ≥2 PMNL/HPF seems to have higher sensitivity in the diagnosis of both GU and NGU.