title: Analysis of percent free prostate-specific antigen (PSA) for prostate cancer detection: influence of total PSA, prostate volume, and age.
abstract: OBJECTIVE
  To determine whether the use of the free-to-total PSA ratio (percent free PSA) could increase the specificity of PSA testing for prostate cancer detection in men with serum PSA concentrations between 4.0 and 10.0 ng/mL, and to assess the influence of total PSA, prostate volume, and age on percent free PSA.
  
  
  METHODS
  Sera were obtained from 217 men with histologically confirmed diagnoses (139 prostate cancer, 78 benign). Free and total PSA concentrations were determined using Hybritech Tandem assays.
  
  
  RESULTS
  Use of percent free PSA increased PSA specificity: 29% of negative biopsies would be spared while retaining 95% sensitivity. Percent free PSA increased with increasing age and prostate volume. Percent free PSA decreased as total PSA increased. A significant relation exists between percent free PSA and the probability of a positive biopsy; in this cohort, a patient with a low percent free PSA (< or = 10%) had a higher probability of cancer (63 +/- 9%) than a patient with a high percent free PSA (> or = 26%) (probability 2 +/- 3%).
  
  
  CONCLUSIONS
  Percent free PSA may be used as an aid in distinguishing prostate cancer from benign disease in men with a total PSA between 4.0 and 10.0 ng/mL. Large prospective multicenter trials are required to develop consistent recommendations and determine the appropriate cutpoints and risk probabilities, controlling for total PSA, prostate volume, age, and biopsy history.
authors.affiliation: Department of Urology, Johns Hopkins Hospital, Baltimore, Maryland, USA.
authors.forename: A W
authors.initials: AW
authors.lastname: Partin
authors.forename: W J
authors.initials: WJ
authors.lastname: Catalona
authors.forename: P C
authors.initials: PC
authors.lastname: Southwick
authors.forename: E N
authors.initials: EN
authors.lastname: Subong
authors.forename: G H
authors.initials: GH
authors.lastname: Gasior
authors.forename: D W
authors.initials: DW
authors.lastname: Chan
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000097:blood / Q000175:diagnosis; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis*; D012044:Regression Analysis; D012307:Risk Factors; D012680:Sensitivity and Specificity
chemical_list: D017430:Prostate-Specific Antigen