Correlations between the human sperm-hamster egg penetration assay and in vitro fertilization results

The human sperm-hamster egg penetration assay (SPA) has been used to evaluate male fertility under in vivo conditions. The test is not only unstandardized, but agreement does not exist as to the lower limits of normal penetration rates. Therefore, it is not surprising that there is considerable doubt as to whether any correlation exists between SPA results and the behavior of sperm in an in vitro laboratory situation. We investigated this question by examining the SPA results and the subsequent fertilization and cleavage rates in the in vitro fertilization program at Pennsylvania Hospital. The sperm from men whose SPA results were 11% or more fertilized 86% of the morphologically normal and mature human oocytes to which they were exposed. Men whose SPA scores ranged from 1% through 10% fertilized 65% of human oocytes, and men whose sperm failed to penetrate hamster eggs still were able to fertilize 41% of the human oocytes. The differences between these groups are statistically significant. This information can be of practical prognostic value during in vitro fertilization cycles in which the number of mature oocytes seen ultrasonographically appears to be at a minimum.