Medical Matters: More technology and less tolerance paves the way for overdiagnosis

Can doctors overdiagnose? At first glance it seems like a silly question. Surely diagnosis is one of our prime functions as medics? Patients expect it and not making a diagnosis would seem to be a slippery slope to poor care and perhaps even negligence.

Counterintuitively, however, there is now a movement towards preventing overdiagnosis, which can be narrowly defined as occurring when people are diagnosed with conditions that will never cause symptoms or shorten their life-spans. It also touches on broader issues such as over-medicalisation, over-treatment and disease mongering and the effect they can have on essentially healthy individuals.

There are many factors potentially driving overdiagnosis: new technology in the form of scans and novel blood tests; less tolerance of medically unexplained symptoms by doctors and patients; higher levels of litigation against doctors driving some to over-investigate; and, of course, the media and greater access to the internet.

Last month a major conference, Preventing Overdiagnosis, took place in New Hampshire. One issue to feature was a recent drive by governments in both the US and the UK to screen older people for minor memory changes (labelled pre-dementia) leading to concerns of unnecessary investigation and potentially harmful treatment for what is arguably an inevitable consequence of ageing.

British and Australian specialists said expanding diagnosis of dementia could result in almost 65 per cent of the population over 80 having Alzheimer's disease diagnosed – and up to 23 per cent of non-demented older people being classed as having dementia.

Ignores the risks
They argue this policy is not backed by evidence and ignores the risks, harms and costs to individuals, families and societies. It may also divert resources that are badly needed for the care of people with advanced dementia. But evidence suggests that as much as 70 per cent of people with mild cognitive impairment will not progress to dementia; indeed, for some, their cognitive function may actually improve.

An important aspect of overdiagnosing dementia is that there aren’t drugs to prevent its progression or which are effective in patients with mild cognitive impairment, raising concerns that once patients are labelled with pre-disease, they may try untested therapies putting them at risk of adverse effects.

Screening for disease is a common bugbear among those who advocate against overdiagnosis. The authoritative US National Cancer Institute (NCI) has even got involved saying that many cancers of the breast, prostate, lung and thyroid would never cause harm during a patient's lifetime.The authors of an NCI report recommended reducing low- yield diagnostics tests, focusing on high-risk populations, reducing screening frequency and raising thresholds for recall and biopsy.

Untreated
They even suggested confining the term cancer to one that describes abnormalities with a reasonable likelihood of causing death if left untreated.

Another diagnosis I would not have expected to come under the spotlight at the recent conference, was that of pulmonary embolism (lung clots). It seems deaths from the condition have remained steady for decades despite increasing testing using Cat scans.This increase has been associated with overdiagnosis of what the presenters called clinically inconsequential pulmonary emboli (PE). These PE were firmly in the sights of Dr Francis Nelson, the GP continuing medical education (CME) tutor for Co Donegal, when he gave a presentation on overdiagnosis to a meeting of the national tutors network recently.

“Historically pulmonary embolism was only diagnosed when the blockage was large enough to cause infarction of part of the lung or haemodynamic instability,” he said. “However, as modern Cat pulmonary angiography can detect smaller clots, there is uncertainty whether treatment is needed.”

The focus on overdiagnosis and subsequent over-treatment is bound to be controversial and brings to mind the quote from Sir William Osler: "One of the first duties of a physician is to educate the masses not to take medicine."

mhouston@irishtimes.com
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