title: [Usefulness of free prostate specific antigen in the detection of prostate cancer].
abstract: BACKGROUND
  The predictive value of prostate specific antigen for prostate cancer, when levels are between 4 and 10 ng/ml, is low. Within these range of values, some authors recommend the measurement of the free fraction of the antigen to improve its predictive capacity.
  
  
  OBJECTIVE
  To evaluate the predictive value of the free fraction in subjects with prostate specific antigen values between 4 and 10 ng/ml.
  
  
  METHODS
  One hundred and forty subjects with prostate specific antigen between 4 and 10 ng/ml were evaluated. All were subjected to transcrectal ultrasound examination with biopsies and the free fraction of the antigen was measured by enzyme immuno assay.
  
  
  RESULTS
  Cancer was diagnosed in 36 subjects, all others had a benign prostatic hyperplasia. Mean prostate specific antigen values were 7.4 and 7.1 ng/ml in patients with cancer and hyperplasia, respectively. The percentage of free prostatic specific antigen was 9.8 and 19.8% in subjects with cancer and hyperplasia respectively (p < 0.001). Using receiver operating characteristic (ROC) curves, a free prostate specific antigen of 13% was the best cutoff value for predicting prostate cancer.
  
  
  CONCLUSIONS
  In subjects with prostate specific values between 4 and 10 ng/ml, the measurement of the free fraction of this antigen can improve the predictive value of this parameter for the detection of prostate cancer.
authors.affiliation: Unidad de Urología, Clínica Santa María. gazocar@rdc.cl
authors.forename: G
authors.initials: G
authors.lastname: Azócar
authors.forename: O
authors.initials: O
authors.lastname: Castillo
authors.forename: R
authors.initials: R
authors.lastname: Van Cauwelaert
authors.forename: M A
authors.initials: MA
authors.lastname: Cumsille
authors.forename: J M
authors.initials: JM
authors.lastname: Campero
authors.forename: C
authors.initials: C
authors.lastname: Aguirre
authors.forename: C
authors.initials: C
authors.lastname: Wöhler
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000097:blood / Q000175:diagnosis*; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis*; D012372:ROC Curve; D012680:Sensitivity and Specificity
chemical_list: D017430:Prostate-Specific Antigen
vernacular_title: Utilidad de la fracción libre del antígeno prostático específico en la detección del cáncer de la próstata.