title: Intra-individual variation of serum prostate specific antigen levels in men with benign prostate biopsies.
abstract: OBJECTIVE
  To determine the intra-individual (physiological) variation of prostate-specific antigen (PSA) measurements in men after a benign prostatic biopsy.
  
  
  METHODS
  Sixty-four men were prospectively assessed, all of whom had a benign prostatic biopsy within the preceding 13 months. The degree of intra-individual variability was established by calculating the coefficient of variation on four PSA levels obtained from each patient weekly over a month.
  
  
  RESULTS
  Six patients were subsequently diagnosed with prostate cancer and their data are presented separately. In the remaining 58 patients the median (range) individual mean PSA value was 6.3 (0.5-34.1) ng/mL. The median (range) coefficient of variation within the group was 9.5 (2.4-76.1)%. There was a clear linear relationship between mean PSA level and the standard deviation.
  
  
  CONCLUSIONS
  In 48 of the 63 patients analysed, the coefficient of variation for serum PSA values in the group as a whole was greater than the variation claimed for the assay technique. The significance of the linear relationship between PSA and the standard deviation is discussed, with particular reference to those men who had a benign prostate biopsy.
authors.affiliation: Department of Urology, Royal Berkshire and Battle Hospital, Oxford Road, Reading RG30 1AG, UK. boddyjane@hotmail.com
authors.forename: J L
authors.initials: JL
authors.lastname: Boddy
authors.forename: S
authors.initials: S
authors.lastname: Dev
authors.forename: D J
authors.initials: DJ
authors.lastname: Pike
authors.forename: P R
authors.initials: PR
authors.lastname: Malone
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001706:Biopsy / Q000379:methods; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D011467:Prostate / Q000473:pathology*; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood*; D012016:Reference Values; D012680:Sensitivity and Specificity
chemical_list: D017430:Prostate-Specific Antigen