title: Why determine only the total prostate-specific antigen, if the free-to-total ratio contains the information?
abstract: BACKGROUND
  Total prostate-specific antigen (tPSA) is the best available test for the detection of prostate cancer but it lacks specificity. The free-to-total ratio (F/T ratio) is used to increase specificity in the range of tPSA of 4-10 microg/L.
  
  
  METHODS
  Four hundred and seven biopsy results and quantitative tPSA and F/T ratio data were combined. Using the histological determination, normal/hyperplasia versus malignant as a gold standard, receiver operating characteristic (ROC) curves as well as the areas under the curve (AUC) for tPSA and F/T ratio were determined. The differences between the two AUCs were considered for various tPSA ranges and specificities of F/T ratio and tPSA were calculated.
  
  
  RESULTS
  In the total group, there was a gain of specificity of 11% (from 23% to 34%) when the sensitivity was 92% (using a cut-off >0.28 for the F/T ratio and a cut-off >4 microg/L for tPSA). When considering the group of patients for which the F/T ratio is currently used (4-10 microg/L), the gain of specificity was 27% (from 2% to 29%). This implicates that the number of unnecessary biopsies taken will be reduced by 27%. Moreover, the AUC of the F/T ratio was significantly higher at an even broader range of tPSA, i.e. up to 40 microg/L.
  
  
  CONCLUSIONS
  This study demonstrates that the F/T ratio has better diagnostic performance than tPSA, not only in the grey zone of tPSA, but also outside the grey zone, i.e. up to 40 microg/L.
authors.affiliation: Dr Bernard Verbeeten Institute, Tilburg, The Netherlands. eekers.d@bvi.nl
authors.forename: Daniëlle Berty Petra
authors.initials: DB
authors.lastname: Eekers
authors.forename: Andrea
authors.initials: A
authors.lastname: Laschet
authors.forename: Monique
authors.initials: M
authors.lastname: de Groot
authors.forename: Erik
authors.initials: E
authors.lastname: Roelofs
authors.forename: Arnold
authors.initials: A
authors.lastname: Kester
authors.forename: Karl
authors.initials: K
authors.lastname: Delaere
authors.forename: Philippe
authors.initials: P
authors.lastname: Lambin
authors.forename: Francis
authors.initials: F
authors.lastname: van Gils
authors.forename: Marius
authors.initials: M
authors.lastname: Nap
authors.forename: Joop
authors.initials: J
authors.lastname: ten Kate
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D006801:Humans; D008297:Male; D008875:Middle Aged; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000097:blood / Q000175:diagnosis; D011471:Prostatic Neoplasms / Q000097:blood / Q000175:diagnosis*; D012016:Reference Values; D012189:Retrospective Studies; D012680:Sensitivity and Specificity
chemical_list: D017430:Prostate-Specific Antigen