The microsperm penetration assay: development of a sperm penetration assay suitable for oligospermic males.

OBJECTIVE

To develop a specialized sperm penetration assay (SPA) for the evaluation of sperm from oligospermic patients.

DESIGN

The development of the assay is in four parts: determine optimal sperm number; demonstrate quality control; establish statistical limits for fertile population; compare results to in vitro fertilization (IVF) outcome.

SETTING AND PATIENTS

A group of 63 patients with oligospermia and/or poor motility and a group of 17 fertile donors were compared using the optimized SPA and the micro-SPA. Sperm from a third group of 35 patients were simultaneously incubated with human ova (IVF) and hamster ova (micro-SPA).

MAIN OUTCOME MEASURES

Both types of SPA scores are expressed as a sperm capacitation index (penetrations per ovum). Outcome of IVF is expressed as a percent of ova fertilized.

RESULTS

Using 25,000 sperm was found to be optimal. The normal fertile range was statistically determined to have a lower limit (-2 SD) of 2.0 penetrations per ovum. When scores from 63 male factor patients were compared using the optimized SPA, only 43% had sufficient swim-up sperm. However, the micro-SPA could accurately test 100% of the samples because it requires only one tenth the number of sperm.

CONCLUSION

The micro-SPA provides a valuable diagnostic test for the evaluation of the male factor patient.