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- Page navigation anchor for Re: Overdiagnosis: causes and consequences in primary health careRe: Overdiagnosis: causes and consequences in primary health care
Shared decision-making can only take place if patients are given accurate information about benefits and harms. For mammography screening, we have contemporary Canadian observational data showing 40% mortality reduction among screened women, starting at age 40 (1). This is much more relevant that the mortality reduction shown in RCTs done 30-50 years ago using mammography equipment that is now obsolete. Additional benefits of early detection are not measured in RCTs: option of lumpectomy instead of mastectomy, sentinel node biopsy instead of axillary dissection, and the possibility to avoid chemotherapy (2, 3). Over-diagnosis is a complicated subject. Drs. Yaffe and Pritchard discuss the issues in simple terms (4), and explain that estimates of overdiagnosis vary widely depending on whether corrections for baseline incidence trends and lead time are performed. When these corrections are applied, overdetection estimates fall into the range of 1%–10% (5).
In an explanation easily understood by patients, they describe overdiagnosis using smoke alarms as an analogy:
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“You spend some money to install the detector(cost and time invested in screening). For most people, there will never be a fire in the house (only about 12% of women will develop breast cancer). If you are lucky in that way, then after the fact, you can think of the investment in the smoke detector as a
waste of money. It is also possible that a fire will start and the detector will not go off fo...Competing Interests: None declared.