Acrosomal morphology as a novel criterion for male fertility diagnosis: relation with acrosin activity, morphology (strict criteria), and fertilization in vitro.

OBJECTIVE

To determine the relationships between sperm acrosin activity, sperm morphology evaluated according to strict criteria, visually observed acrosomal morphology, and IVF rates.

DESIGN

Prospective analytic study. Acrosin activity was determined on all semen samples together with a standard semen analysis. Emphasis was placed on sperm morphology and especially a novel criterion viz acrosome morphology (acrosome index) as recorded with bright field microscopy.

SETTING

University-based tertiary care center.

PATIENTS

Thirty-three couples undergoing IVF or GIFT with two or more metaphase II ova inseminated in vitro.

MAIN OUTCOME MEASURE

In vitro fertilization rates of inseminated ova.

RESULTS

Strong correlations were found between acrosome index, normal sperm morphology, and IVF rates. An acrosome index cutoff value could be established at > 10% normal acrosomes for IVF rates of > or = 50% (sensitivity and specificity = 100%) and an acrosin activity cutoff value at > 18 microIU/10(6) sperm. A multiple linear regression analysis showed that the acrosome index and acrosin activity added a significant contribution to the explanation of the variation in the fertilization rates.

CONCLUSIONS

A strong positive correlation was found between acrosome index and IVF rates. Although the numbers of the study are small, the results indicate that the acrosome index possibly may be regarded as an additional tool in the prediction of IVF outcome and especially may be of value in the group of men with severe teratozoospermia, i.e., < or = 4% morphologically normal spermatozoa.