title: Total sperm per ejaculate of men: obtaining a meaningful value or a mean value with appropriate precision.
abstract: We retrospectively mined and modeled data to answer 3 questions. 1) Relative to an estimate based on approximately 20 semen samples, how imprecise is an estimate of an individual's total sperm per ejaculate (TSperm) based on 1 sample? 2) What is the impact of abstinence interval on TSperm and TSperm/h? 3) How many samples are needed to provide a meaningful estimate of an individual's mean TSperm or TSperm/h? Data were for 18-20 consecutive masturbation samples from each of 48 semen donors. Modeling exploited the gamma distribution of values for TSperm and a unique approach to project to future samples. Answers: 1) Within-individual coefficients of variation were similar for TSperm or TSperm/h abstinence and ranged from 17% to 51%; average approximately 34%. TSperm or TSperm/h in any individual sample from a given donor was between -20% and +20% of the mean value in 48% of 18-20 samples per individual. 2) For a majority of individuals, TSperm increased in a nearly linear manner through approximately 72 hours of abstinence. TSperm and TSperm/h after 18-36 hours' abstinence are high. To obtain meaningful values for diagnostic purposes and maximize distinction of individuals with relatively low or high sperm production, the requested abstinence should be 42-54 hours with an upper limit of 64 hours. For individuals producing few sperm, 7 days or more of abstinence might be appropriate to obtain sperm for insemination. 3) At least 3 samples from a hypothetical future subject are recommended for most applications. Assuming 60 hours' abstinence, 80% confidence limits for TSperm/h for 1, 3, or 6 samples would be 70%-163%, 80%-130%, or 85%-120% of the mean for observed values. In only approximately 50% of cases would TSperm/h for a single sample be within -16% and +30% of the true mean value for that subject.
  
  
  CONCLUSIONS
  Pooling values for TSperm in samples obtained after 18-36 or 72-168 hours' abstinence with values for TSperm obtained after 42-64 hours is inappropriate. Reliance on TSperm for a single sample per subject is unwise.
authors.affiliation: Animal Reproduction and Biotechnology Laboratory, Colorado State University, Fort Collins, Colorado, USA. rpalra62@comcast.net
authors.forename: Rupert P
authors.initials: RP
authors.lastname: Amann
authors.forename: Phillip L
authors.initials: PL
authors.lastname: Chapman
mesh_terms: D004542:Ejaculation / Q000502:physiology*; D006801:Humans; D008297:Male; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012661:Semen / Q000166:cytology*; D012746:Sexual Abstinence; D013076:Sperm Count / Q000379:methods*; D013094:Spermatozoa; D013997:Time Factors; D014019:Tissue Donors