title: Methods of calculating prostate-specific antigen velocity.
abstract: OBJECTIVE
  Numerous methods of calculating PSA velocity (PSAV) are used and have the potential to produce differing PSAV results from the same PSA data. We calculated PSAV using three common methods and compared differences between the methods and their predictive value for prostate cancer diagnosis.
  
  
  METHODS
  From a population-based database of PSA results, men with initial PSA<10.0 ng/ml and a subsequent diagnosis of prostate cancer or benign histology were identified. Those with > or =3 PSA tests before diagnosis carried out over a minimum of 18 mo were included. PSAV was calculated by using three methods: The differences between the methods and test characteristics of each method were compared.
  
  
  RESULTS
  Of the 2204 men included, 716 (32.5%) were diagnosed with prostate cancer and 1488 (67.5%) benign histology. PSAV differed markedly in each method of calculation. The LR and FL methods had similar predictive values, which were higher than the AE method. There was strong agreement for cancer diagnosis between LR and FL (kappa=0.85), with weaker agreement between LR/AE and FL/AE (kappa=0.69 and 0.66, respectively).
  
  
  CONCLUSIONS
  Methods used to calculate PSAV using the same PSA data can produce markedly different results. Linear regression should be the method of choice for calculating PSAV. Using first and last PSA values only may be adequate for everyday clinical use, as long as measurements are separated by a sufficiently long time period.
authors.affiliation: Department of Urology, Belfast City Hospital, Belfast, Northern Ireland, United Kingdom. djconn76@hotmail.com
authors.forename: David
authors.initials: D
authors.lastname: Connolly
authors.forename: Amanda
authors.initials: A
authors.lastname: Black
authors.forename: Liam J
authors.initials: LJ
authors.lastname: Murray
authors.forename: Giulio
authors.initials: G
authors.lastname: Napolitano
authors.forename: Anna
authors.initials: A
authors.lastname: Gavin
authors.forename: Patrick F
authors.initials: PF
authors.lastname: Keane
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood; D006801:Humans; D008297:Male; D008875:Middle Aged; D009660:Northern Ireland / Q000453:epidemiology; D017430:Prostate-Specific Antigen / Q000097:blood / Q000378:metabolism*; D011469:Prostatic Diseases / Q000453:epidemiology; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000453:epidemiology*; D012680:Sensitivity and Specificity
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen