Background: Various methods for the selection of viable sperm from among immotile testicular spermatozoa for use in ICSI have been described in non-randomized studies. We have conducted a randomized controlled study to compare the use of the modified hypo-osmotic swelling (HOS) test (50% culture medium + 50% Milli-Q grade water) with that of sperm selection on the basis of their morphology alone.
Methods: A total of 79 couples with immotile testicular spermatozoa treated with ICSI were randomly assigned into two groups. In the first group, spermatozoa used for injection were selected using the modified HOS test, while in the second group spermatozoa were selected on the basis of their morphology.
Results: The fertilization rate was significantly higher in the HOS test group (43.6%) compared with the no-HOS test group (28.2%) [odds ratio (OR) 2.494; 95% confidence interval (CI) 1.606-3.872]. The pregnancy and ongoing pregnancy rates were also higher in the HOS test group (27.3% versus 20.5%) compared with the no-HOS test group (5.7% versus 2.9%) (OR 6.188, 95% CI 1.282-29.860; and OR 8.743, 95% CI 1.050-72.783, respectively).
Conclusions: The use of the modified HOS test for the selection of viable sperm from among immotile testicular spermatozoa for ICSI results in higher fertilization, pregnancy and ongoing pregnancy rates compared with morphological selection.