Association between hypo-osmotic swelling test-induced tail swelling patterns and sperm quality

Aim: The current sperm selection procedure for intracytoplasmic sperm injection has limited ability to detect structural and functional abnormalities of the spermatozoa. The aim of this study was to investigate whether the degree of sperm tail swelling observed during hypo-osmotic swelling test (HOST) may predict sperm quality. Materials & methods: Sixty semen samples were collected from men investigated for couple infertility. For each sample, sperm parameters, HOST and sperm chromatin status were evaluated. The relationship between the different HOST-induced tail swelling patterns ('a' to 'g') and sperm quality was evaluated. Results: The HOST significantly correlated with higher sperm motility and vitality, and with better morphology and nuclear quality. The HOST grades 'b' and 'c' were associated with better motility (p < 0.05 and p < 0.01, respectively) and morphology (grade 'b', p < 0.001). While grade 'd' was associated with better motility and count (p < 0.05). Conclusion: Our results show that the pattern of sperm tail swelling is linked to sperm functional integrity. HOST grades 'b' and 'd' were associated with better sperm quality, suggesting their preferential use during routine sperm selection for intracytoplasmic sperm injection.