Subsidised scan seeks to ensure more accurate Alzheimer’s diagnosis

Anastasia Tsirtsakis

12/11/2021 2:21:06 PM

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

A female patient being prepared for a scan.
FDG PET scans have been shown to have a sensitivity of 85%, and a 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 GPs.
A key barrier is the high cost, with patients paying up to $1000 out of their own pocket. But the Federal Government has announced that, as of 1 November, the cost will be subsidised, making the imaging test available through the Medicare Benefits Schedule (MBS).
Professor Christopher Rowe, director of the Australian Dementia Network (ADNeT), has been advocating with Austin Health for seven years to have the technology added to the MBS. He told newsGP that wider access should mean a more accurate, and earlier, diagnosis for patients.
‘Given that this is a devastating disease and ultimately fatal, it’s important to be accurate,’ Professor Rowe said.
‘Clinical diagnosis alone is not able to be made until the patient already has fully established dementia, even though the patient may have presented several years earlier with concerns about their memory and, even then, when you make the diagnosis based on clinical criteria, it is wrong 30% of the time.
‘But with FDG PET there’s a better chance that you can make a more specific diagnosis and give a more accurate prognosis.’
FDG PET scans are not limited to Alzheimer’s disease, but can also help detect other forms of dementia.
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, the scan can reveal patterns as to what may be causing the cognitive impairment.
It is estimated that 472,000 people are living with dementia in Australia, with Alzheimer’s disease accounting for about two-thirds of cases.
Though there is currently no cure, an early diagnosis can ensure people have a better chance of benefiting from treatment and also assist in delaying the onset of severe symptoms.
Professor Dimity Pond, who is a GP with a special interest in aged care and dementia, welcomed news of broader accessibility to FDG PET scans, but said GPs need more information and guidance.
‘GPs haven’t been using PET scans much,’ she told newsGP. ‘So because of that, I think we will all need to get up to speed on the indications for using one.
‘There’ve been quite a lot of advances in imaging techniques for dementia generally, so I’d like to know how well the PET distinguishes between Alzheimer’s disease and other forms of dementia, and I’d also be interested in why we want to make that distinction.’
Professor Pond is concerned the test may have implications for people’s access to treatment. Currently, the cholinesterase inhibitors prescribed for patients with dementia are only indicated for Alzheimer’s disease and requires a clinical diagnosis.
‘So it might be that the use of the PET scans will help to define the group that can benefit or that are allowed to benefit from the anti-dementia drugs,’ Professor Pond said.
‘That raises some other issues about whether in fact there’s good quality evidence that those drugs only work for Alzheimer’s and not for, say, vascular dementia or other forms of dementia.
‘That really needs to be thought through in terms of whether … it’s actually going to result in fewer people being able to access some medications.’
Professor Rowe, however, is optimistic that the technology will help to complement new emerging therapies, which could be available in Australia in a year or two.
‘It’ll be even more important to make accurate and earlier diagnosis before there’s too much damage done,’ he said. ‘So improvements in diagnostic diagnosis are needed, and this is one step in the right direction.’
According to MBS Online, an FDG PET scan for the diagnosis of Alzheimer’s disease can be ordered using item 61560, if ‘clinical evaluation of the patient by a specialist, or in consultation with a specialist, is equivocal’.
While Professor Pond agrees that access to new technology for the diagnosis of 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 well placed to do because we know the patient,’ she said.
Professor Rowe agrees, and says that he does not envisage FDG PET scans to be a routine part of care where the diagnosis is a typical clinical presentation, and ‘glaringly obvious’.
‘However, in patients where the features aren’t typical or where there’s language impairment, or other reasons for not being able to get reliable history or reliable cognitive findings – which is quite often the case – then this will be a very valuable test,’ he said.
‘Also in earlier stages of disease, when somebody’s got mild cognitive impairment, rather than just sit on the fence and wait, you might be able to make a more accurate diagnosis.’
While the sensitivity of FDG PET scans is 85% and the specificity up to 80%, Professor Rowe says that it is not a perfect test. It has limitations, including a less clear result for people over the age of 75 and those with very mild cognitive impairment, where there isn’t much brain disturbance to be detected.
To ensure both clinicians and patients can get the most out of the test, Professor Pond says she anticipates GPs will need to be upskilled in interpreting the results.
As a first step, Professor Rowe has developed two 90-minute tutorials, now available on the on the ADNeT website, including various case studies. 
Federal Health Minister Greg Hunt said the new MBS listing is a significant development for Australians and their families.
‘This listing will benefit thousands of Australians who through early and accurate diagnosis, will be able to seek earlier treatment,’ he said.
‘[It] will also reduce out-of-pocket costs for Australian patients and ensure more affordable access to PET scans and Alzheimer’s diagnosis.’
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Alzheimer’s disease dementia FDG PET scan positron emission tomography

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Dr Arlene Nicol Suttar   16/11/2021 8:53:38 AM

472,000 people having dementia in Australia is not a big number. So caution in opening the option of GPs ordering these PET scans . The stated item number requires the patient to see a specialist geriatrician . They are amazing wonderful specialists who take time usually 1 hour for initial consult, so I feel it should be left in their hands as this is more cost effective than GPs being more free to offer /order one . Patients will learn of the scan and request when worried ,so how many GPs will be " nice" " pressured ' to order them . Just look at the history of MRIs for low back pain with patients wanting them " to see how their back is going ". Lets pause as the medicare money has to go around everyone and be sustainable into the future.