Semen parameters in a fertile versus subfertile population: a need for change in the interpretation of semen testing

This prospectively designed study was conducted to compare a fertile and asubfertile population so as to define normal values for different semenparameters. Semen analyses were performed according to the World HealthOrganization (WHO) guidelines, except for sperm morphology (strictcriteria). In the fertile population (n = 144), all patients had recentlyachieved pregnancy, within 12 months of unprotected coitus. As subfertilecontrols we examined semen samples from 143 consecutive men attending ourinfertility clinic during the same study period. Couples with tubal factorinfertility and/or ovulatory disorders were excluded from our study. Usingreceiver operating characteristic (ROC) curve analysis we determined thediagnostic potential and cut-off values for single and combined spermparameters. Sperm morphology scored best, with a value of 78% (area underthe ROC curve). Summary statistics showed a shift towards abnormality formost semen parameters in the subfertile population. Using the 10thpercentile of the fertile population as the cut-off value, the followingresults were obtained: 14.3 x 10(6)/ml for sperm concentration, 28% forprogressive motility and 5% for sperm morphology. Using ROC analysis,cut-off values were 34 x 10(6)/ml, 45% and 10% respectively. Cut-off valuesfor normality were different from those described in the WHO guidelines.Routine bacterial and non- bacterial cultures turned out to be of littleprognostic value.