Does the hypoosmotic swelling test predict human sperm viability?

Human sperm viability is essential for successful fertilization. Eosin Y is the usually accepted method for sperm viability assessment, though the hypoosmotic swelling test has been proposed for the selection of viable spermatozoa in procedures such as intracytoplasmic sperm injection.;The present study was designed to determine the value of hypoosmotic swelling test in the prediction of sperm viability. For this purpose, hypoosmotic swelling and eosin Y were performed in parallel and in combination, on both fresh and freeze-thawed semen. Rates for eosin Y were significantly higher than for the hypoosmotic swelling test in fresh semen, with a weak, though significant correlation between the two tests (r = 0.47, p < 0.05). When both tests were performed in succession (hypoosmotic swelling test followed by eosin Y). 14.6% of swollen sperm incorporated the dye. Following exposure to hypoosmotic conditions, sperm viability decreased by 35%. When sperm were killed by freezing, hypoosmotic swelling test rates were higher than rosin Y. Results indicate that these two tests cannot bet used interchangeably, since 15% of the swollen sperm apparently died, suggesting that plasma membrane integrity is lost before the capacity to maintain osmotic equilibrium.