Funded analysis seeks to ensure more accurate diagnosis of Alzheimer’s disease

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Positron emission tomography scans have been added to the MBS, but General Professor Dimity Pond says more guidance is needed.

FDG CT scans have been shown to have a sensitivity of 85% and specificity of up to 80%.


When it comes to diagnosing Alzheimer’s disease, 18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) scans are rarely used by general practitioners.

One of the main obstacles is the high cost, with patients paying up to $ 1,000 out of their own pocket. But the federal government has announced that from November 1 the cost will be subsidized, making the imaging test available through the scale of health insurance benefits (MBS).

Professor Christopher Rowe, director of the Australian Dementia Network (ADNeT), has been advocating with Austin Health for the past seven years for the technology to be added to the MBS. He said gp news that wider access should mean more accurate and earlier diagnosis for patients.

“Since this is a devastating and ultimately fatal disease, it is important to be specific,” said Professor Rowe.

“The clinical diagnosis on its own cannot be made until the patient already has fully established dementia, although the patient may have had concerns many years previously about their memory and even then when you ask. the diagnosis on the basis of clinical criteria is wrong 30% of the time.

“But with FDG PET, you are more likely to make a more accurate diagnosis and give a more accurate prognosis. “

FDG PET scans are not limited to Alzheimer’s disease, but can help detect other forms of dementia as well.

It works by measuring the concentration of glucose in the brain to reveal how different parts of the brain are using energy. With different forms of dementia associated with reduced brain activity in specific parts of the brain, analysis can reveal trends as to what may be causing cognitive impairment.

It is estimated that 472,000 people live with dementia in Australia, with Alzheimer’s disease representing about two thirds of cases.

Although there is currently no cure, early diagnosis can ensure that people have a better chance of receiving treatment and also help delay the onset of severe symptoms.

Professor Dimity Pond, who is a general practitioner with a particular interest in elderly care and dementia, welcomed the news of greater accessibility to FDG CT scans, but said GPs needed more information and advice.

“GPs don’t use PET scanners a lot,” she said gp news. “So because of that, I think we’ll all have to make ourselves aware of the indications to use one.

“There has been a lot of advancement in imaging techniques for dementia in general, so I’d like to know how well PET distinguishes Alzheimer’s disease from other forms of dementia, and I would be also interested in why we want to make this distinction.

Professor Pond is concerned that the test may have implications for people’s access to treatment. Currently, cholinesterase inhibitors prescribed to patients with dementia are only indicated for Alzheimer’s disease and require clinical diagnosis.

“It may therefore be that the use of PET scans helps define the group who can benefit or who is entitled to benefit from anti-dementia drugs,” said Professor Pond.

“This raises further questions as to whether there is in fact good quality evidence that these drugs only work for Alzheimer’s disease and not for, say, vascular dementia or other forms of dementia.

“It really needs to be thought through to see if… it’s actually going to reduce the number of people able to access certain drugs.”

Professor Rowe, however, is optimistic that the technology will help complement emerging new therapies, which could be available in Australia in a year or two.

“It will be even more important to make an accurate and early diagnosis before too much damage is done,” he said. “Improvements in diagnostic diagnostics are therefore needed, and this is a step in the right direction.”

According to MBS Online, FDG PET for the diagnosis of Alzheimer’s disease can be ordered using article 61560, if “the clinical evaluation of the patient by a specialist, or in consultation with a specialist, is ambiguous”.

While Professor Pond agrees that access to new technologies for diagnosing dementia is “the way of the future,” she says a history and physical exam will always be crucial.

“I don’t think it will relieve the need for the clinical assessment, which GPs are in a good position to do because we know the patient,” she said.

Professor Rowe agrees and says he does not envision FDG CT scans as part of routine care when the diagnosis is a typical clinical presentation and “overwhelmingly obvious.”

“However, in patients whose characteristics are not typical or in whom there is language impairment, or other reasons for not being able to obtain a reliable history or reliable cognitive results – which is quite often the case – then it will be a very valuable test, ‘he said.

“Also in the early stages of the disease, when someone has mild cognitive impairment, rather than just sitting on the fence and waiting, you may be able to make a more accurate diagnosis.”

While the sensitivity of FDG PET scans is 85% and specificity up to 80%, Professor Rowe says it’s not a perfect test. It has limitations, including a less clear result for people over 75 and those with very mild cognitive impairment, where there aren’t many brain disturbances to detect.

To make sure clinicians and patients can get the most out of the test, Professor Pond says she anticipates GPs will need to be better qualified to interpret the results.

As a first step, Professor Rowe developed two 90-minute tutorials, now available on the the ADNeT website, including various case studies.

Federal Health Minister Greg Hunt said the new MBS list is an important development for Australians and their families.

“This list will benefit thousands of Australians who, through early and accurate diagnosis, will be able to seek treatment sooner,” he said.

‘[It] will also reduce out-of-pocket costs for Australian patients and ensure more affordable access to CT scans and diagnosis of Alzheimer’s disease. ‘

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