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Discrepancy between sperm acrosin activity and sperm morphology: significance for fertilization in vitro.

Langlois MR, Oorlynck L, Vandekerckhove F, Criel A, Bernard D, Blaton V

Andrology Unit, Department of Clinical Chemistry, AZ St-Jan Hospital, Ruddershove 10, B-8000 Bruges, Belgium. michel.langlois@azbrugge.be

BACKGROUND: In routine semen analysis, discrepancies may occur between sperm acrosin activity test results and sperm acrosomal morphology. METHODS: Discrepant test results of sperm acrosin activity (spectrophotometric assay) vs. sperm morphology (strict criteria) in the initial diagnostic investigation of 107 infertile couples were evaluated with respect to fertilization rate (% oocytes with 2 pronuclei) further obtained in IVF treatment. RESULTS: Acrosin activity positively correlated with sperm morphology (% normal forms) (r=0.537) and fertilization rate (r=0.526). ROC curves for the prediction of > or =50% fertilization rate were comparable for acrosin activity and sperm morphology, with optimal cutoff values at 25 microIU/10(6) sperm and 10%, respectively. In multiple regression analysis, sperm acrosin activity (P=0.002) predicted fertilization rate independently of sperm morphology (P<0.001) and sperm vitality (eosin-nigrosin stain) (P=0.03). Acrosin activities > or =25 microIU/10(6) sperm were observed in 36% of severe teratozoospermic samples (< or =4% normal spermatozoa) associated with low fertilization rate. Twenty percent of the morphologically normal ejaculates showed a low acrosin activity (<25 microIU/10(6) sperm) and low hypoosmotic swelling test (HOST) scores (31.4+/-7.6%) and were associated with low fertilization rate. CONCLUSION: The sperm acrosin assay can help to predict sperm fertilizing capacity in IVF independently of sperm morphology.

Published 26 November 2004 in Clin Chim Acta, 351(1): 121-9.
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