Intra- and inter-individual variability in human sperm concentration, motility and vitality assessment during a workshop involving ten laboratories

The aim of the present study was to assess variability in the evaluation of human sperm concentration, motility and vitality, Technicians and biologis ts from 10 teams involved in multicentre studies on semen quality attended the same laboratory, each team using its own methods and equipment to analy se the same semen samples. Inter-individual variability was assessed from 1 7 fresh semen samples of varying quality. Intra-individual variability was assessed from pools of frozen samples for sperm concentration and motility and stained smears for vitality with three blind evaluations by sample and smear. The mean inter-individual coefficients of variation mere 22.9, 21.8 and 17.5% for sperm concentration, motility and vitality respectively. Ther e was no statistical difference among participants for sperm concentration assessment, but significant differences for both motility and vitality (bot h P < 0.05). The mean intraindividual coefficients of variation were 15.8, 26.2 and 13.1% for sperm concentration, motility and vitality respectively, with marked differences between expert and novice participants: concentrat ion 9.8% versus 28.0%; motility 22.8% versus 33.0%; and vitality 10.0% vers us 19.3%. The present data confirm the need for external quality control sc hemes for diagnostic purposes, and indicate their utmost importance in mult icentre studies on semen quality.