Individual variation in semen parameters of healthy young volunteers.

Individual variation in semen parameters was investigated in healthy young volunteers. Semen samples were collected approximately once a month over a one-year period for a total of 93 samples (5 to 10 samples per subject) from 12 volunteers in their twenties. Semen analysis was carried out according to the WHO Manual. The amount of variation in each semen variable was calculated for each subject by dividing the maximum value by the minimum value. The results showed that the semen volume varied by 1.9+/-0.8 fold (1.3 to 4.2 fold), the sperm concentration by 4.8+/-4.3 fold (1.5 to 17.2 fold), the percentage of sperm with forward progression by 2.8+/-1.4 fold (1.6 to 6.4 fold), the percentage of sperm with rapid linear progression by 3.4+/-2.6 fold (1.7 to 10.9 fold), the percentage of sperm with normal morphology by 1.9+/-0.4 fold (1.3 to 2.4 fold), and the percentage of live sperm by 1.5+/-0.4 fold (1.1 to 2.6 fold). A between-group comparison showed significant differences in all of the variables except the percentage of sperm with normal morphology. These results suggest multiple and considerable semen analyses are needed when evaluating semen parameters.