Objective: To assess if patients who do not fertilize human oocytes in vitro can be identified by a lack of acrosomal response of their spermatozoa to stimulation by the calcium ionophore A23187.
Design: The stimulated acrosomal response for all patients was calculated. Those not achieving fertilization were compared with a normogram constructed from donors and patients who achieved fertilization; the 0.5th centile (31.3% increase in the number of spermatozoa reacted) was used as a discriminant point.
Patients: Fifty-four IVF patients and 15 fertile sperm donors.
Setting: An outpatient based IVF program.
Interventions: Acrosome reaction stimulated by 2 hours incubation in a 5-mumol/L solution of the calcium ionophore A23187.
Results: Patients who fertilized oocytes responded as donors. Eight of 16 patients failing to fertilize oocytes showed a minimal increase in the number of acrosome-reacted spermatozoa (mean [+/- SD] rise 6.3% +/- 10.3%). An acrosomal response of < 31.3% predicts fertilization failure in 100% of cases.
Conclusions: Failure of the acrosome to react is responsible for some failure of IVF.