Limit testing to curb epidemic of overdiagnosis


There are no quick and easy answers to the growing problem of overdiagnosis however clinicians can start by adopting a judicious approach to screening and diagnostic tests, an expert advises.

Speaking to the limbic after a presentation at the RCPA’s Pathology Update in Sydney recently, Professor Paul Glasziou reminded doctors of the potential to do more harm than good.

“If you do lots of tests, you will discover things you don’t need to know,” he said.

“We need to stick to proven screening tests that have been shown to have an impact.”

He said screening for ovarian cancer, prostate cancer or abdominal aortic aneurysms fell outside evidence-based guidelines such as the Redbook Guidelines for Preventive Activities in General Practice.

Professor Glasziou, Professor of Evidence-Based Medicine at Bond University, said the thyroid cancer controversy – a three-fold increase in thyroid cancer detection and a parallel rise in thyroidectomy – highlighted one of the problems of overdetection and overdiagnosis.

“Once you label something as a cancer, people will want to do something about it. Most people find it distressing to watch and wait.”

He said other than the ‘mania’ for thyroid function tests, many thyroid cancer cases were discovered as a consequence of ultrasonography of the carotid or a chest CT scan.

He said other cases of overdiagnosis were driven by competing definitions of disease or thresholds for tests that did not reflect the true impact on the individual.

For example, the fact an estimated glomerular filtration rate (eGFR) was not in the same range as a 30 year-old, did not necessarily mean an older person’s kidneys would not last their lifetime.

“In the elderly, half the population are now defined as having stage 3A chronic kidney disease instead of a very normal decline in renal function.”

Professor Glasziou said pathologists could help address overdiagnosis by improving the interpretation of test results.

“They can certainly influence the need for subsequent tests by recommendations for or against further tests or repeat tests,” he said.

“Certainly overmonitoring can also lead to overdiagnosis as eventually you will get false positives.”

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