COMPARISON OF RAT EPIDIDYMAL SPERM COUNTS BY IVOS HTM-IDENT AND HEMACYTOMETER

Epididymal sperm counts, a common measurement in male reproductive tox icity studies, are routinely determined using a hemacytometer. Recentl y, computer assisted methods for automated sperm counts have been deve loped. In the present study we evaluated an automated system, the TOX IVOS (Hamilton Thorne Research, Beverly, MA) HTM-IDENT option, that ut ilizes a DNA-specific stain and fluorescence illumination to identify sperm for enumeration, Cauda and caput epididymal sperm counts were de termined in 48 adult male Sprague-Dawley rats, using both the hemacyto meter and HTM-IDENT. The mean hemacytometer and HTM-IDENT counts (+/- SD) were 250 +/- 43 and 254 +/- 52 million, respectively, for cauda sp erm, and 123 +/- 13 and 127 +/- 18 million, respectively, for caput sp erm. The average coefficient of variation using the hemacytometer was 13.8% as compared to 17.3% for the HTM-IDENT. Comparison of the machin e count and a visual count from the Display Statics screen of the HTM- IDENT indicated that when two or more sperm heads touched or overlappe d, the machine counted them as one. Manual (visual) and machine counts when compared over a range of nine concentrations from 3.7 to 47.8 mi llion/mL differed by 4 to 12% at the lowest to highest concentration. The concentration of epididymal sperm samples used in comparing the tw o counting methods ranged from 5.8 to 17.7 million/mL. Therefore, the HTM-IDENT undercounting error attributable to sperm heads touching was less than 6%. Overall the data indicate good agreement between the HT M-IDENT and the hemacytometer counts. Furthermore, both counting time and technician fatigue were markedly reduced. Thus the HTM-IDENT optio n improves the efficiency of epididymal sperm counting without loss of precision.