Objective: To determine within-and between-subject variation of semen parameters in infertile and normal men. Design: Retrospective analysis of 74 infertile men and 65 normal men producing five or more ejaculates each. Setting: Clinical andrology laboratory. Subject(s): Men presenting to an infertility clinic for semen analysis and normal men providing donor semen for cryopreservation. Intervention(s): None. Main Outcome Measure(s): Within-subject coefficients of variation (CVw) and between-subject coefficients of variation (CVb), calculated for sperm count, motility, and velocity, semen volume, and motility and velocity after cryopreservation. Result(s): The number of ejaculates ranged 5-20 in patients (479 total) and 5-136 in donors (2,043 total). Sperm counts, motility, and velocity were statistically greater in donors, whereas semen volume was significantly greater in patients. The CVw in patients and donors was greatest in sperm counts (54.2%and 45.8%, respectively)-and lowest in velocity (20.1%and 19.9%, respectively). The CVb in patients and donors was markedly higher than CVw for all parameters in both patients and donors. The CVw was lower, and the CVb was higher, in donors compared with patients. The CVw was not affected by age of the individual or abstinence period. Cryopreservation resulted in a marked increase in variability. Intraclass correlations indicated that a minimum of three semen samples were required to achieve reliability. Conclusion(s): These data indicate large within-and between-subject variation in sperm parameters, especially sperm count, in both patients and healthy donors, and further substantiate the need for measurement of multiple ejaculates before characterizing a man as normal or infertile.
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