Sperm Vitality

Sperm vitality is an important test, especially for samples with less than about 40% progressively motile sperms. The percentage of live spermatozoa is assessed by identifying those with an intact cell membrane, from dye exclusion or by     hypotonic swelling. The dye exclusion method is based on the principle that damaged plasma membranes, such as those found in non-vital (dead) cells, allow entry of membrane-impermeant stains. The hypo-osmotic swelling test presumes that only cells with intact membranes (live cells) will swell in hypotonic solutions. Sperm vitality should be assessed as soon as possible after liquefaction of the semen sample, preferably at 30 minutes, but in any case, within 1 hour of ejaculation, to prevent observation  of deleterious effects of dehydration or of changes in temperature on vitality. It is clinically important to know whether immotile spermatozoa are alive or dead. Vitality results should be assessed in conjunction with motility results from the same semen sample. The presence of a large proportion of vital but immotile cells may be indicative of structural defects in the flagellum. A high percentage of immotile and non-viable cells  may indicate epididymal pathology.