New approach to microscopy of Gram-stained urethral smear: the kissing slide method.

BACKGROUND The effectiveness of microscopy of Gram-stained smear (GSS) for the detection of male urethral infection is debatable, especially in cases with low inflammation and no visible urethral discharge. This clinical study compared GSS samples collected with the conventional swab method and our new technique, the kissing slide method, together with PCR results to demonstrate the effectiveness of this new method in men with acute urethritis. METHODS The study included 64 men who presented to the urology outpatient clinic with complaints of acute urethritis between October 2019 and January 2020. Two GSS samples were collected from each patient, first using the kissing slide method (applying the slide directly to the urethral mucosa), followed by the conventional method. The results were compared with PCR findings. RESULTS The patients' mean age was 37.4±7.8 years, and 68.7% had no visible urethral discharge on physical examination. At a GSS threshold of ≥5 PMNL/HPF, sensitivity was 60% (95% CI: 42.32-75.41) for the kissing slide method and 23.33% (95% CI: 11.79-40.93) for the conventional method. At a threshold of ≥2 PMNL/HPF, sensitivity with the kissing slide and conventional methods were 80% (95% CI: 62.69-90.5) and 50% (95% CI: 33.15-66.85) in all patients, and 66.67% (95% CI: 41.71-84.82) and 20% (95% CI: 7.047-45.19) in cases without visible urethral discharge, respectively. CONCLUSION The new kissing slide method is a noninvasive alternative method that may have better sensitivity than the conventional GSS sampling method in the diagnosis of male acute urethritis. Randomized studies are needed to verify these findings.