Clinical significance of human sperm-zona pellucida binding.

To assess the relationship between sperm morphology and motion parameters and sperm-zona pellucida (ZP) binding capacity under hemizona assay (HZA) conditions and to determine the discriminatory power of the HZA for the prediction of in vitro sperm fertilizing ability. Prospectively designed study. Academic tertiary centers. One hundred ninety-six couples undergoing IVF therapy participated in this study. Hemizona assay and IVF results were determined for each couple. Computerized sperm motion analysis, sperm morphology (strict) criteria), and HZA results were correlated with fertilization outcome. Among sperm parameters from the original ejaculates, morphology was the best predictor of sperm-ZP binding ability; hyperactivated motility was the best predictor of HZA results after swim-up separation of the motile sperm fractions. The HZA index provided the highest discriminatory power for fertilization success/failure, with an overall accuracy of 86%. Sperm morphology and hyperactivated motility showed a high correlation with the capacity of sperm to achieve tight binding to the ZP. The excellent positive and negative predictive values of the HZA for fertilization outcome provide additional support for the use of this functional bioassay in the decision-making process within the assisted reproduction setting.