title: False-positive screening results in the Finnish prostate cancer screening trial.
abstract: BACKGROUND
  There is evidence that prostate cancer (PC) screening with prostate-specific antigen (PSA) serum test decreases PC mortality, but screening has adverse effects, such as a high false-positive (FP) rate. We investigated the proportion of FPs in a population-based randomised screening trial in Finland.
  
  
  METHODS
  Finland is the largest centre in the European Randomized Study of Screening for Prostate Cancer. We have completed three screening rounds with a 4-year screening interval (mean follow-up time 9.2 years) using a PSA cutoff level of 4.0 ng ml(-1); in addition, men with PSA 3.0-3.9 and a positive auxiliary test were referred. An FP result was defined as a positive screening result without cancer in biopsy within 1 year from the screening test.
  
  
  RESULTS
  The proportion of FP screening results varied from 3.3 to 12.1% per round. Of the screened men, 12.5% had at least one FP during three rounds. The risk of next-round PC following an FP result was 12.3-19.7 vs 1.4-3.7% following a screen-negative result (depending on the screening round), risk ratio 3.6-9.9. More than half of the men with one FP result had another one at a subsequent screen. Men with an FP result were 1.5 to 2.0 times more likely to not participate in subsequent rounds compared with men with a normal screening result (21.6-29.6 vs 14.0-16.7%).
  
  
  CONCLUSIONS
  An FP result is a common adverse effect of PC screening and affects at least every eighth man screened repeatedly, even when using a relatively high cutoff level. False-positive men constitute a special group that receives unnecessary interventions but may harbour missed cancers. New strategies are needed for risk stratification in PC screening to minimise the proportion of FP men.
authors.affiliation: Department of Urology, University of Tampere and Tampere University Hospital, Box 2000, Tampere FIN-33521, Finland. tuomas.kilpelainen@uta.fi
authors.forename: T P
authors.initials: TP
authors.lastname: Kilpeläinen
authors.forename: T L J
authors.initials: TL
authors.lastname: Tammela
authors.forename: L
authors.initials: L
authors.lastname: Määttänen
authors.forename: P
authors.initials: P
authors.lastname: Kujala
authors.forename: U-H
authors.initials: UH
authors.lastname: Stenman
authors.forename: M
authors.initials: M
authors.lastname: Ala-Opas
authors.forename: T J
authors.initials: TJ
authors.lastname: Murtola
authors.forename: A
authors.initials: A
authors.lastname: Auvinen
mesh_terms: D000368:Aged; D001706:Biopsy; D055088:Early Detection of Cancer; D005189:False Positive Reactions; D005387:Finland; D006801:Humans; D008297:Male; D008403:Mass Screening; D008875:Middle Aged; D011467:Prostate / Q000473:pathology; D017430:Prostate-Specific Antigen / Q000097:blood*; D011470:Prostatic Hyperplasia / Q000188:drug therapy; D011471:Prostatic Neoplasms / Q000175:diagnosis*
chemical_list: D017430:Prostate-Specific Antigen