title: Do physicians understand cancer screening statistics? A national survey of primary care physicians in the United States.
abstract: BACKGROUND
  Unlike reduced mortality rates, improved survival rates and increased early detection do not prove that cancer screening tests save lives. Nevertheless, these 2 statistics are often used to promote screening.
  
  
  OBJECTIVE
  To learn whether primary care physicians understand which statistics provide evidence about whether screening saves lives.
  
  
  METHODS
  Parallel-group, randomized trial (randomization controlled for order effect only), conducted by Internet survey. (ClinicalTrials.gov registration number: NCT00981019)
  
  
  METHODS
  National sample of U.S. primary care physicians from a research panel maintained by Harris Interactive (79% cooperation rate).
  
  
  METHODS
  297 physicians who practiced both inpatient and outpatient medicine were surveyed in 2010, and 115 physicians who practiced exclusively outpatient medicine were surveyed in 2011.
  
  
  METHODS
  Physicians received scenarios about the effect of 2 hypothetical screening tests: The effect was described as improved 5-year survival and increased early detection in one scenario and as decreased cancer mortality and increased incidence in the other.
  
  
  METHODS
  Physicians' recommendation of screening and perception of its benefit in the scenarios and general knowledge of screening statistics.
  
  
  RESULTS
  Primary care physicians were more enthusiastic about the screening test supported by irrelevant evidence (5-year survival increased from 68% to 99%) than about the test supported by relevant evidence (cancer mortality reduced from 2 to 1.6 in 1000 persons). When presented with irrelevant evidence, 69% of physicians recommended the test, compared with 23% when presented with relevant evidence (P < 0.001). When asked general knowledge questions about screening statistics, many physicians did not distinguish between irrelevant and relevant screening evidence; 76% versus 81%, respectively, stated that each of these statistics proves that screening saves lives (P = 0.39). About one half (47%) of the physicians incorrectly said that finding more cases of cancer in screened as opposed to unscreened populations "proves that screening saves lives."
  
  
  CONCLUSIONS
  Physicians' recommendations for screening were based on hypothetical scenarios, not actual practice.
  
  
  CONCLUSIONS
  Most primary care physicians mistakenly interpreted improved survival and increased detection with screening as evidence that screening saves lives. Few correctly recognized that only reduced mortality in a randomized trial constitutes evidence of the benefit of screening.
  
  
  BACKGROUND
  Harding Center for Risk Literacy, Max Planck Institute for Human Development.
authors.affiliation: Harding Center for Risk Literacy, Max Planck Institute for Human Development, Berlin, Germany. wegwarth@mpib-berlin.mpg.de
authors.forename: Odette
authors.initials: O
authors.lastname: Wegwarth
authors.forename: Lisa M
authors.initials: LM
authors.lastname: Schwartz
authors.forename: Steven
authors.initials: S
authors.lastname: Woloshin
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Gaissmaier
authors.forename: Gerd
authors.initials: G
authors.lastname: Gigerenzer
mesh_terms: D002983:Clinical Competence; D055088:Early Detection of Cancer / Q000706:statistics & numerical data*; D006801:Humans; D009369:Neoplasms / Q000453:epidemiology / Q000401:mortality; D058007:Physicians, Primary Care; D010818:Practice Patterns, Physicians'; D011795:Surveys and Questionnaires; D015996:Survival Rate; D014481:United States / Q000453:epidemiology