Doctors Often Misunderstand the Science Behind Screening Tests
Here’s another arrow in the quiver of patients well-armed against deficiencies in (well-meaning but often wrong) preventive medical care.
A survey published in the Annals of Internal Medicine concluded that primary care doctors can be as confused as the rest of us when they ponder information about screening tests.
“Most primary care physicians mistakenly interpreted improved survival and increased detection with screening as evidence that screening saves lives,” the authors wrote. “Few correctly recognized that only reduced mortality in a randomized trial constitutes evidence of the benefit of screening.”
An accompanying editorial in the same publication claimed that what physicians don’t know can harm their patients, and that screening for things such as breast and prostate cancer are widely overused.
Not that we love saying, “We told you so,” but we told you so.
As reported on MedPage Today, in a hypothetical scenario, about 3 in 4 physicians incorrectly said that increased five-year survival and early detection of cancer proves that a screening test saves lives. About 8 in 10 correctly said that a reduction in mortality in a randomized trial proves the efficacy of a screening test.
According to the study authors, "Misunderstanding of statistics ... matters, because it may influence how physicians discuss screening with their patients or how they teach trainees."
The researchers explained how measuring survival rates can be subject to bias. In a group of individuals who will die at 70, the five-year survival rate for those diagnosed with cancer because of symptoms they had at 67 will be 0 percent. But the five-year survival rate for those diagnosed through screening at 60 will be 100 percent.
"Yet, despite this dramatic improvement in survival ... nothing has changed about how many people die or when," they said.
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