Objective: To assess the value of different sperm function screening tests in predicting fertilization.
Design: Prospective study.
Setting: Academic tertiary referral center for fertility treatment.
Patients: Ninety-five couples attending for initial screening and IVF-ET. Only cycles where three or more grade I oocytes were collected were included, and patients with endometriosis were excluded.
Interventions: Each patient had a standard semen analysis, cervical mucus (CM) penetration test, hypo-osmotic swelling test, and sperm migration test performed between 4 and 8 weeks before IVF-ET.
Main outcome measures: The correlation between sperm function test results and the percentage of fertilized oocytes and the power of the tests to predict fertilization.
Results: The sperm migration test correlated highly with fertilization rate (r = 0.62) and was most useful in identifying the group of patients likely to achieve fertilization (Odds ratio [OR] 0.07, confidence interval [CI] 0.02 to 0.2). The CM penetration test showed a moderate correlation with fertilization rate (r = 0.45) and some predictive power (OR 0.37, CI 0.13 to 1.00). Sperm concentration, but not motility or normal morphology, showed slight correlation with fertilization rate (r = 0.28) but the combination of normal semen parameters did not distinguish patients likely to achieve fertilization (OR 1.51, CI 0.62 to 3.65). The hypo-osmotic swelling test did not correlate with fertilization rate (r = 0.21).
Conclusions: This study evaluated the predictive power of several simple tests available for use in most laboratories as screening tests of sperm fertilization potential. Apart from sperm concentration, normal traditional semen characteristics were of little clinical benefit. The hypo-osmotic swelling test had no predictive power. The CM penetration test correlated with fertilization rate but might be difficult to perform routinely as a continuous supply of suitable CM would be required. The sperm migration test proved to be the best discriminator of sperm fertilization potential and should be considered as a first level screening test in the assessment of male fertility.