Assessment of heterospecific zona-free ovum penetration under fully defined conditions

The prognostic value of the sperm penetration assay (SPA) using zona-free hamster ova has not been universally accepted. This is partly due to technical problems with the assay, resulting in 5-17% false negative results. The advantage of replacing albumin with defined synthetic polymers in the SPA culture media, increasing the calcium gradient and incorporating potential active tract agents and antioxidants, has been investigated. These studies have resulted in the development of a procedure that has produced no negative results among known fertile donors (n = 55). Application of this technique to a non-specific group of patients with suspected sub-fertility produced a different pattern of sperm penetration compared with the 'standard' SPA in 27% of cases. Improved sperm velocity, motile survival, enhanced hyaluronidase release and rate of acrosome induction were noted using the synthetic media.