title: Prostate-specific antigen velocity before and after elimination of factors that can confound the prostate-specific antigen level.
abstract: OBJECTIVE
  Prostate-specific antigen (PSA) velocity, like PSA level, can be confounded. In this study, we estimated the impact that confounding factors could have on correctly identifying a patient with a PSA velocity >2 ng/ml/y.
  
  
  METHODS
  Between 2006 and 2010, a total of 50 men with newly diagnosed PC comprised the study cohort. We calculated and compared the false-positive and false-negative PSA velocity >2 ng/ml/y rates for all men and those with low-risk disease using two approaches to calculate PSA velocity. First, we used PSA values obtained within 18 months of diagnosis; second, we used values within 18 months of diagnosis, substituting the prebiopsy PSA for a repeat, nonconfounded PSA that was obtained using the same assay and without confounders.
  
  
  RESULTS
  Using PSA levels pre-biopsy, 46% of all men had a PSA velocity >2 ng/ml/y; whereas this value declined to 32% when substituting the last prebiopsy PSA for a repeat, nonconfounded PSA using the same assay and without confounders. The false-positive rate for PSA velocity >2 ng/ml/y was 43% as compared with a false-negative rate of PSA velocity >2 ng/ml/y of 11% (p = 0.0008) in the overall cohort. These respective values in the low-risk subgroup were 60% and 16.7% (p = 0.09).
  
  
  CONCLUSIONS
  This study provides evidence to explain the discordance in cancer-specific outcomes among groups investigating the prognostic significance of PSA velocity >2 ng/ml/y, and highlights the importance of patient education on potential confounders of the PSA test before obtaining PSA levels.
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Boston, MA 02115, USA. park16@fas.harvard.edu
authors.forename: Jessica J
authors.initials: JJ
authors.lastname: Park
authors.forename: Ming-Hui
authors.initials: MH
authors.lastname: Chen
authors.forename: Marian
authors.initials: M
authors.lastname: Loffredo
authors.forename: Anthony V
authors.initials: AV
authors.lastname: D'Amico
mesh_terms: D000368:Aged; D001706:Biopsy; D015986:Confounding Factors, Epidemiologic; D005188:False Negative Reactions; D005189:False Positive Reactions; D006801:Humans; D008297:Male; D008875:Middle Aged; D011379:Prognosis; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000378:metabolism*; D011471:Prostatic Neoplasms / Q000378:metabolism* / Q000401:mortality / Q000473:pathology; D013997:Time Factors
chemical_list: D017430:Prostate-Specific Antigen