The use of semen parameters to identify the subfertile male in the general population
Aims: To present a structured review of the literature published on semen parameters and in vivo fertility potential and to establish fertility/ subfertility thresholds for sperm morphology using Tygerberg strict criteria, sperm concentration, and sperm motility. Method: The published literature comparing fertile and subfertile populations between 1983 and 2002 was reviewed. Results: A total of 265 articles were identified by the sourcing methodology, but only four articles provided data that could be tabulated and analyzed. Using receiver-operating characteristics curves, morphology proved to be the best predictor of subfertility in 2 of the 4 articles, with concentration and motility also showing good predictive power. The thresholds calculated ranged between 4 and 10% for morphology, between 13.5 × 106/ml and 34 × 106/ml for concentration, and between 32 and 52% for motility. A second set of much lower thresholds was calculated in three of the articles using either a 15 or 50% prevalence of subfertility in the population or the tenth percentile of the fertile population. The adjusted thresholds were between 3 and 5% for morphology, between 9 × 106/ml and 20 × 106/ml for concentration, and between 20 and 30% for motility. Conclusions: Because these lower thresholds have a much higher positive predictive value, we suggest that thresholds of <5% normal sperm morphology, a concentration <15 × 106/ml, and a motility <30% should be used to identify the subfertile male. The lower threshold for morphology also fits in vitro fertilization and intrauterine insemination data calculated previously. Using the parameters in combination increases the clinical value of semen analysis. Copyright © 2005 S. Karger AG.