title: Intraindividual variation in total and percent free prostate-specific antigen levels in prostate cancer suspects.
abstract: OBJECTIVE
  To investigate intraindividual total and percent free serum prostate-specific antigen (PSA) in prostate cancer suspects and to understand the clinical implications.
  
  
  METHODS
  Total and percent free PSA were measured using Tandem-R or chemiluminescent enzyme-linked immunoassay for a median of three times in 126 men. Prostate biopsies were performed in all patients; benign prostatic hyperplasia was diagnosed in 81 patients and prostate cancer in 45 patients.
  
  
  RESULTS
  The overall mean coefficients of variation for total and percent free PSA were 16.10 +/- 11.94% and 15.45 +/- 15.91%, respectively. A significant correlation (p = 0.0056) was observed between the two variations. The variations in total and percent free PSA were related to none of such stratifications as baseline total PSA level, histology, age, or measurement interval, but for measurement interval on that for total PSA.
  
  
  CONCLUSIONS
  Intraindividual variation in serum PSA should be considered in decision-making about performing prostate biopsies. Also, care should be taken in interpreting repeated percent free PSA measurements in order to enhance the specificity of total PSA, because it had a similar variation to total PSA variation.
authors.affiliation: Department of Urology, Jichi Medical School, Kawachi-gun, Tochigi, 329-0498, Japan. minoruk@jichi.ac.jp
authors.forename: Minoru
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Shinsuke
authors.initials: S
authors.lastname: Kurokawa
authors.forename: Akihiko
authors.initials: A
authors.lastname: Tokue
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000097:blood; D001706:Biopsy; D006801:Humans; D007124:Immunoenzyme Techniques; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000097:blood / Q000473:pathology; D011471:Prostatic Neoplasms / Q000097:blood* / Q000473:pathology; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen