CH Muller, RE Berger, JN Krieger
Male Fertility Laboratory and Prostatitis Clinic, Department of Urology, University of Washington, Seattle, WA
Introduction To distinguish men with inflammatory (category Illa) from those with non-inflammatory (category Illb) chronic abacterial prostatitis/chronic pelvic pain syndrome (CPPS), a method must accurately detect
and allow quantitation of leukocytes (WBC) in expressed prostatic secretions (EPS). Based on laboratory experience and current methodologies, we suspected that wet mount examination of EPS would be inaccurate and
therefore of limited quantitative value in this respect.
Methods Three methods for microscopic evaluation of EPS leukocytes were compared in 251 samples from 159 patients with CPPS: (1) Traditional
cover-slipped (wet mount) slide; (2) Hemacytometer; and (3) Smear of EPS stained with DiffQuick. Multiple evaluations of individual samples were used to assess variation and volume effects.
Inflammation defined as 2500 WBC/mm3 was identified in 149 (59%) of the 251 specimens by hemacytometer, but in only 82 (33%) of the same specimens by wet mount, using 210 WBC /400x hpf as the critical value (McNemar's
Chi Square p<O.001). Using a critical value of 21000 WBC/ mm3, 121 (48%) of samples were classified as inflamed by hemacytometer (p<0.001 compared to wet mount). Inflammation defined as 22 WBC /50 1000x hpf was
detected in 147 (59%) of specimens by DiffQuick- stained smears. In 159 initial patient evaluations, 84 (53%) had inflammation by hemacytometer, but only 37 (23%) were considered inflamed by the coverslip method
(p<0.001). Most importantly, the hemacytometer method had substantially lower inter- and intra-assay coefficients of variation than the coverslip method, and the latter exhibited a linear relationship between volume
of EPS placed on the slide and number of WBC/hpf. Polymorphonuclear neutrophils and macrophages were the most commonly observed leukocytes based on DiffQuick staining.
Conclusions Significantly more cases of
inflammation were detected by hemacytometer than by the traditional coverslip method. Because the coverslip method also proved more variable than hemacytometer, and highly sensitive to volume, its use is not
recommended. Stained smears do not allow accurate quantitation, but are essential for cell identification. These findings support adoption of hemacytometer and staining methods for accurate evaluation of EPS
inflammation in men with CPPS.
Supported by NIH Grant R01 DK38955 and by the Paul G. Allen Foundation for Medical Research