title: Proposal for a standardized PSA doubling-time calculation.
abstract: OBJECTIVE
  Prostate-specific antigen (PSA) doubling-time (PSA-DT) is an important indicator of progression and survival in men with prostate cancer. Three major limitations regarding PSA-DT determination may lead to inconsistent results: the variety of mathematical methods currently applied, the non-standardized handling of input variables and the potential lack of accuracy due to PSA variability. The aim of this project was to develop a reproducible PSA-DT determination tool which simultaneously provides a PSA-DT error estimation.
  
  
  METHODS
  An internet-based PSA-DT calculation tool via nonlinear optimization implementing the least squares error method using the most recent three PSA values was developed. PSA-DT calculation error is estimated via randomly disturbed measurement data streams (n=65) based on a variable (5-25%) PSA variability.
  
  
  RESULTS
  According to a simulation in five men, PSA-DT was calculated to be between 1.7 and 15 month (mean: 6.3 month) and determined with another standard tool between 1.3 and 14.5 month (mean: 4.2 month).
  
  
  CONCLUSIONS
  We present a defined, open and reproducible PSA-DT calculation and PSA-DT error estimation tool based on a standardized PSA data input. This tool is not better compared to other methods but is scientifically standardized and freely accessible via the following internet address: http://adam.drahtwarenhandlung.at/webapp/mg2008/chapter_prostata4/example_psa.
authors.affiliation: Department of Urology and Andrology, Danube Hospital, Vienna, Austria. anton.ponholzer@wienkav.at
authors.forename: Anton
authors.initials: A
authors.lastname: Ponholzer
authors.forename: Nikolaus
authors.initials: N
authors.lastname: Popper
authors.forename: Felix
authors.initials: F
authors.lastname: Breitenecker
authors.forename: Hans-Peter
authors.initials: HP
authors.lastname: Schmid
authors.forename: Walter
authors.initials: W
authors.lastname: Albrecht
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Loidl
authors.forename: Stephan
authors.initials: S
authors.lastname: Madersbacher
authors.forename: Paul
authors.initials: P
authors.lastname: Schramek
authors.forename: Axel
authors.initials: A
authors.lastname: Semjonow
authors.forename: Michael
authors.initials: M
authors.lastname: Rauchenwald
mesh_terms: D014408:Biomarkers, Tumor / Q000096:biosynthesis; D019411:Clinical Laboratory Techniques; D015331:Cohort Studies; D003627:Data Interpretation, Statistical; D006801:Humans; D007700:Kinetics; D016018:Least-Squares Analysis; D008297:Male; D008962:Models, Theoretical; D011379:Prognosis; D017430:Prostate-Specific Antigen / Q000096:biosynthesis*; D011471:Prostatic Neoplasms / Q000097:blood* / Q000175:diagnosis*; D015203:Reproducibility of Results; D013997:Time Factors
chemical_list: D014408:Biomarkers, Tumor; D017430:Prostate-Specific Antigen