Sperm acrosin activity may be a useful factor in choosing between ICSI and IVF for infertile male patients.

The clinical applications of acrosin activity are limited. We analyzed 61 578 male partners in infertile couples who visited the outpatient department of the Reproductive and Genetic Hospital of CITIC-Xiangya (Changsha, China) between August 2014 and December 2019 to determine the reference ranges and thresholds for acrosin activity in infertile Chinese men; to determine whether correlations exist between acrosin activity and age, sperm concentration, sperm morphology, or sperm motility; and to evaluate whether acrosin activity could serve as an effective prognostic indicator for choosing between in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) in the clinic. The cut-off value for the normal reference range of acrosin activity for male partners in infertile couples was 24.78 µIU per 10 6 sperm. There was no significant association between acrosin activity and age, sperm concentration, semen volume, total sperm count, progressive motility, or total motile spermatozoa. A weak positive correlation was found between acrosin activity and normal sperm morphology. There was a statistically significant difference in abnormal acrosome morphology between the group with high acrosin activity (>24.78 µIU per 10 6 sperm) and the group with low acrosin activity (<24.78 µIU per 10 6 sperm). The group with a low IVF fertilization rate had a high index of abnormal acrosomal morphology at 21.2%, while the group with a high IVF fertilization rate had a low index of 0.2%. At an acrosin activity of <24.78 µIU per 10 6 sperm, in one cycle of the same patient, the fertilization rate, normal fertilization rate, and good-quality embryo rate for ICSI were significantly higher than those for IVF. Therefore, the most promising application of acrosin activity could be in the selection of ICSI over IVF for infertile male patients with complete fertilization failure or a low fertilization rate.