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Expanding the measurement of overdiagnosis in the context of disease precursors and risk factors
  1. Guylene Theriault1,
  2. Donna Reynolds2,3,
  3. Jennifer J Pillay4,
  4. Heather Limburg5,
  5. Roland Grad1,
  6. Michelle Gates4,
  7. Frantz-Daniel Lafortune1,6,
  8. Pascale Breault6,7
  1. 1 Department of Family Medicine, McGill University, Montreal, Quebec, Canada
  2. 2 Department of Family and Community Medicine, University of Toronto, Toronto, Ontario, Canada
  3. 3 Dalla Lana School of Public Health, University of Toronto, Toronto, Ontario, Canada
  4. 4 Faculty of Medicine and Dentistry, University of Alberta, Edmonton, Alberta, Canada
  5. 5 Global Health and Guidelines Division, Public Health Agency of Canada, Ottawa, Ontario, Canada
  6. 6 Department of Family Medicine, Universite Laval, Quebec, Quebec, Canada
  7. 7 Department of Family Medicine, Universite de Montreal, Montreal, Quebec, Canada
  1. Correspondence to Dr Guylene Theriault, Department of Family Medicine, McGill University, Montreal, QC H3S 1Z1, Canada; guylene.theriault{at}

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Because individual patients weigh benefits and harms differently, it is important to provide quantitative information about the benefits and harms of screening interventions, particularly when benefits and harms are in equipoise.1 The goal of this article is to help clinicians have a more fulsome understanding of the implications of different screening situations. Guideline developers may also find this helpful when estimating the magnitude of overdiagnosis in screeningwhere the outcome is not overt disease.

Many clinicians discuss the potential benefits and harms of screening with their patients. But without an estimate of their magnitude, it is difficult to engage patients in shared decision making (SDM). One recognised harm of screening is overdiagnosis which ‘means making people patients unnecessarily, by identifying problems that were never going to cause harm’.2 Although its magnitude has been much debated, there is little debate about the existence of overdiagnosis in screening.3 Overdiagnosis estimates are mostly available in screening for overt disease (eg, cancer). Here, we propose a method to make such estimates in the context of screening for disease precursors and risk factors for disease.

Screening can identify non-disease conditions such as the risk of an outcome (eg, risk of a fragility fracture) or potential precursors of disease (eg, colonic polyps). In these instances, the measurement of the extent of overdiagnosis is a challenge that has not yet been clearly addressed. For overdiagnosis in risk assessment, we are not aware of any attempt to define the concept nor provide an estimate of its magnitude. For precursors of disease, some authors have described overdiagnosis in colon cancer screening4 or used modelling to estimate overdiagnosis of precancerous cervical lesions.5 Building on these reflections, we first outline the measurement of overdiagnosis in overt disease, and then propose a conceptual model and a method to …

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  • Contributors Clinical practice guidelines support primary care providers in delivering preventive health services and diagnosing disease. For providers to have meaningful discussions with their patients, basic information is needed on the potential benefits and harms of receiving a diagnosis, including the harm of overdiagnosis. While developing guidelines on screening interventions, we realised that the concept of overdiagnosis was harder to grasp outside of the context of cancer screening. For example, overdiagnosis is harder to conceptualise in the context of screening to prevent fragility fracture, as this process yields a risk of future fracture. Similarly, screening for cervical or colon cancer mainly results in detection of precancerous lesions which has implications on incidence of diseases. This article discusses these challenges in the understanding of overdiagnosis.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; internally peer reviewed.