title: A meta-analysis of the performance characteristics of the free prostate-specific antigen test.
abstract: OBJECTIVE
  To conduct a meta-analysis of the diagnostic performance of the percent free prostate-specific antigen (%fPSA) test in determining prostate cancer status and to assess its value in helping to decide whether to biopsy the prostate.
  
  
  METHODS
  Articles identified through a MEDLINE search were included if they presented adequate original primary data to calculate a receiver operating characteristic (ROC) curve in subjects possessing histopathologically verified diagnoses. Articles containing subjects with concurrent, non-prostate-related genitourinary conditions were excluded. Percent free PSA sensitivity, specificity, ROC curves, and positive likelihood ratios were calculated for all PSA ranges and for the reflex range of PSA between 4 and 10 ng/mL.
  
  
  RESULTS
  Among the 41 studies, containing 19,643 subjects, area under the curve for %fPSA was 0.70 for all PSA levels, decreasing to 0.68 in the reflex range. A test cutoff of 20% would lead to 92% sensitivity and 23% specificity. Positive likelihood ratios ranged from 1.0 to 4.0, exceeding 2.0 at %fPSA of 15% or less. Within the reflex range, however, likelihood ratios exceeded 2.0 only at %fPSA of 7% or less.
  
  
  CONCLUSIONS
  Percent free PSA can be a useful adjunct to PSA for primary prostate cancer screening only under certain defined situations. In the "gray zone," or reflex range, of PSA testing, %fPSA improves clinical information only when levels reach extreme values.
authors.affiliation: Department of Urology, New York Presbyterian Hospital, Weill Cornell Medical College, New York, New York 10021, USA. ril9010@nyp.org
authors.forename: Richard
authors.initials: R
authors.lastname: Lee
authors.forename: A Russell
authors.initials: AR
authors.lastname: Localio
authors.forename: Katrina
authors.initials: K
authors.lastname: Armstrong
authors.forename: S Bruce
authors.initials: SB
authors.lastname: Malkowicz
authors.forename: J Sanford
authors.initials: JS
authors.lastname: Schwartz
mesh_terms: D001774:Blood Chemical Analysis / Q000592:standards; D006801:Humans; D008297:Male; D017430:Prostate-Specific Antigen / Q000097:blood*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis; D012680:Sensitivity and Specificity
chemical_list: D017430:Prostate-Specific Antigen