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Ann Intern Med. 2012 Mar 6;156(5):340-9. doi: 10.7326/0003-4819-156-5-201203060-00005.

Do physicians understand cancer screening statistics? A national survey of primary care physicians in the United States.

Author information

  • 1Harding Center for Risk Literacy, Max Planck Institute for Human Development, Berlin, Germany. wegwarth@mpib-berlin.mpg.de

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.

DESIGN:

Parallel-group, randomized trial (randomization controlled for order effect only), conducted by Internet survey. (ClinicalTrials.gov registration number: NCT00981019)

SETTING:

National sample of U.S. primary care physicians from a research panel maintained by Harris Interactive (79% cooperation rate).

PARTICIPANTS:

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.

INTERVENTION:

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.

MEASUREMENTS:

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."

LIMITATION:

Physicians' recommendations for screening were based on hypothetical scenarios, not actual practice.

CONCLUSION:

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.

PRIMARY FUNDING SOURCE:

Harding Center for Risk Literacy, Max Planck Institute for Human Development.

Comment in

PMID:
22393129
[PubMed - indexed for MEDLINE]
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