Mannose ligand receptor assay as a test to predict fertilization in vitro: a prospective study.

To assess whether mannose receptor assays can predict fertilization outcome in vitro. A prospective, double-blind study of the mannose receptor properties of spermatozoa. Assisted human reproduction program at a university hospital. Partners of 140 consecutive women undergoing their first in vitro fertilization cycle. Motile sperm populations were tested for surface receptors for mannose by measuring their ability to bind fluorescein-labeled mannosylated albumin and to undergo a free mannose-induced acrosome reaction as judged by Pisum, sativum agglutinin binding. Mannose receptor assay results were correlated with fertilization outcomes using several statistical tests, including the chi2 test, chi2 for proportions, t-tests, analysis of variance with Student-Newman-Keuls tests and correlational and receiver operating characteristic (ROC) curve analysis. The fractional increment increase on incubation in the percent of sperm binding mannose ligand over an intact acrosome correlated with fertilization rates in vitro. Threshold values of mannose ligand binding and of mannose-induced acrosome reactions predictive of fertilization rates were identified by ROC curve analysis. Men were thus classified into one of four groups with differing fertilization rates in vitro. The increment increase in sperm surface mannose ligand binding by acrosome-intact sperm correctly predicts high and low fertilization rates in vitro and identifies cases where conventional insemination can result in failed fertilization.