Sperm penetration assay: useful test in evaluation of male fertility.

The recently developed sperm penetration assay (SPA) tests the functional capacity of sperm. It is based upon the ability of in vitro capacitated human spermatozoa to penetrate zona-free hamster eggs in vitro. The SPA was superior to seminal fluid analysis in predicting both fertility and infertility; in the prediction of infertility, the difference was highly significant. Data further indicated that fertility in the male may not remain constant with the passage of time. The SPA would appear to have wide application both clinically and experimentally.