Comparison of centrifugation- and noncentrifugation-based techniques for recovery of motile human sperm in assisted reproduction.

To compare standard density gradient centrifugation sperm preparation with a novel non-centrifugation-based dual-chamber capillary dish in efficiency for motile human sperm separation, approximately 3 mL fresh ejaculate specimens was obtained from 21 men (median age = 32 years. range 26-42 years) undergoing infertility evaluation. For each specimen, half of the sample was processed with a standard 45%/90% density gradient preparation (PureSperm. Nidacon International, Gothenburg, Sweden) followed by semen analysis. The other half was incubated in the Zech glass capillary dish (Astromedtec, Salzburg, Austria) consisting of 2 concentric wells overlaid by a U-ring and coverglass. After approximately 3 h, a 1-mL sample was taken from the central chamber and analyzed. Percentage motile sperm recovery, absolute (motile) cell number, and path velocities were compared for spermatozoa obtained from both methods. Both techniques reduced overall sperm concentration while enriching specimens with more motile spermatozoa. A trend towards higher % recovery of motile spermatozoa (p = .264) was observed with the Zech device, but at a cost of fewer absolute numbers of higher velocity cells (p = .004). The Zech device, therefore, localized a very small population of motile sperm without exposure to centrifugation stress, which has been considered potentially harmful to spermatozoa. This technique could theoretically improve efficiency by reducing time required to identify motile cells in in vitro fertilization where intracytoplasmic sperm injection is planned. However, refinements in incubation interval and suspension volumes are needed before this technique can be considered comparable to the density gradient method in recovering sperm for use in intrauterine insemination.