The sperm penetration test (P-test) can predict fecundability in the male partner from infertile couples

Three hundred and twenty-one consecutive couples were investigated for infertility at Hvidovre University Hospital in the period from November 1977 to June 1985. The male partners were evaluated in two ways: the classical semen analysis, and the ability of sperm to penetrate fresh hen egg white, the P-test. A Cox regression analysis was used to describe the relation between these variables and fecundability, i.e. the time required to conceive. Four of thirteen variables--the number of morphologically normal spermatozoa, the number of motile spermatozoa, the P-test, and the man's age--each have significant relation to the fecundability. However, when covariation is considered, only the P-test and the man's age possess significant prognostic information, whereas the variables of the classical semen analysis do not. This indicates that the P-test may replace the classical semen analysis when trying to predict individual pregnancy probabilities. Finally, the P-test and the man's age are combined to form a prognostic index which predicts the fecundability of the male partner in the individual infertile couple.