Hypoosmotic swelling test in normo-, oligo-, astheno- and oligoasthenozoospermic men before and after swim-up separation of spermatozoa

Semen samples from a total 58 men were examined by routine semen analyses and the hypoosmotic swelling test. Samples were classified as normal, oligo-, astheno- or oligoasthenozoospermic on the basis of spermatogram findings. The latter three groups showed a significant decrease in the percentage of HOS positive forms in comparison to normal spermograms. All these samples were treated with the swim up technique to select motile spermatozoa, using a procedure similar to that routinely employed in clinical settings for homologous intrauterine insemination (IUI). Following swim-up, the ejaculate supernatant and residual precipitate were subjected to the hypoosmotic swelling test (HOS test), and the percentage of normal forms was determined in the three groups. The results showed greater percentages of HOS positive, normal and HOS positive-normal forms in the group of normal individuals than in any of the other three groups. The supernatant used in IUI showed a significant increase in percentage HOS positive spermatozoa, normal forms and spermatozoa which were both normal and HOS positive in comparison with the other two groups in normal and oligozoospermic samples, but not in samples which presented suboptimal motility (astheno- and oligozoospermia). In conclusion, the swim-up technique is effective in separating high-quality spermatozoa in normo- and oligozoospermic samples, although its effectiveness with astheno- and oligoasthenozoospermic samples should be questioned.