Comparison of microscopic methods for detecting inflammation in expressed prostatic secretions

Purpose: We evaluated microscopic methods of detecting inflammation in expressed prostatic secretions. Materials and Methods: Methods of counting expressed prostatic secretion leukocytes were compared in 251 samples from 159 patients with chronic prostatitis/chronic pelvic pain syndrome, including traditional wet mounts, hemocytometer derived concentrations and expressed prostatic secretion smears stained with Gram's method or DiffQuick stain (Dade International, Inc., Miami, Florida). Results: Of 159 initial patient evaluations 84 (53%) showed inflammation by hemocytometer concentration at 500 leukocytes per mm.(3) or greater but only 37 (23%) were considered inflammation by the traditional wet mount method (p < 0.001). Inflammation was identified in 149 of 251 specimens (59%) by hemocytometer but in only 82 (33%) by wet mount (p < 0.001). When inflammation was defined as 1,000 leukocytes per mm.3 or greater the hemocytometer still identified significantly more patients (41%) and specimens (48%) with inflammation than the wet mount. The hemocytometer method had a substantially lower interassay and intro-assay coefficient of variation than the wet mount method. Polymorphonuclear neutrophils and macrophages were the most common cells observed on stained smears, which detected inflammation in 147 specimens (59%) by DiffQuick but in only 98 (39%) by Gram's method. Conclusions: Detecting inflammation in expressed prostatic secretions is method dependent. Significantly more cases of inflammation were detected by hemocytometer than by the traditional wet mount technique. Because the wet mount method also proved more variable than the hemocytometer and highly sensitive to volume, its use is not recommended. These findings support the adoption of hemocytometer and staining methods for accurate evaluation of expressed prostatic secretion inflammation in men with chronic prostatitis/chronic pelvic pain syndrome.