Which is the best test to evaluate the integrity of sperm plasma membrane?

The functional integrity of sperm plasma membrane of 87 semen samples collected from fertile and infertile men was assessed by the hypoosmotic swelling test (HOS). The results were correlated with sperm motility and supravital stains using trypan blue and eosin Y. These data indicate that sperm swelling and staining methods evaluate different properties of spermatozoa. Moreover the present report shows that staining percentages with trypan blue are significantly lower than with eosin Y