Amyloid proteins in normal brains (left) and abnormal ones (right) visualized with GE Healthcare’s PET tracer flutemetamol.
Alzheimer’s disease is the commonest cause of dementia, and as the population is aging, it’s prevalence is increasing.
Alzheimer’s disease presently affects 5 million Americans aged 65 or older. Without a major medical breakthrough, by 2025 this number is expected to have risen to 7 million, and by 2050 it could reach 14 million
The costs of caring for Alzheimer’s patients is also increasing, estimated at $203 billion in 2013, and $1.2 trillion by 2050, including a 500% increase in combined Medicare and Medicaid spending.
Clearly, finding that major therapeutic breakthrough is crucial, and had been identified as a priority by the Obama Administration.
The first barrier to starting any clinical trial is accurate case ascertainment – we have to be able to correctly identify early Alzheimer’s patients for new experimental treatments.
So far, the only definitive test for Alzheimer’s disease is examination of brain tissue (usually obtained at autopsy) for identification of the characteristic pathologic changes of Amyloid paque and Neurofibrillary tangles:
Alzheimer’s disease is usually diagnosed based on clinical criteria, but many patients diagnosed this way are later found to have other causes of dementia when their brains are examined at autopsy, in other words they were misdiagnosed as Alzheimer’s.
With more research trials and potential new effective therapies on the horizon, it is going to become more important to establish a diagnosis of Alzheimer’s more accurately and earlier, perhaps even pre-symptomatically (i.e. mild cognitive impairment or MCI), so that treatment to reverse the build up of plaque and tangles is more likely to be effective.
New positron emission tomography (PET) technology can actually quantify the amount of amyloid in affected patients’ brains. A recently published small study showed a very high correlation between amyloid identified on PET scans and amyloid plaque demonstrated in brain biopsy specimens taken from demented patients.
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These tests are going to be very important for research studies.
However, don’t rush to your private doctor’s office asking to have one done just yet!
Although approved by the FDA, these test are not yet covered by Medicare or other insurance covering, and cost between $1500 and $3000.
Furthermore, these are new tests, and their role in clinical neurology practice in still unclear.
Some of these issues were recently clarified in a report by the Amyloid Imaging Taskforce convened by the Alzheimer’s Association and the Society of Nuclear Medicine and Molecular Imaging:
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This taskforce concluded that a Amyloid PET scan is indicated for:
Progressive memory impairment or dementia with atypical features, where a positive PET would indicate definite Alzheimer’s, and a negative scan would rule it out and lead to further testing for other possible causes.
Younger patients (aged 50-65) with suspected Alzheimer’s, in whom making a definitive diagnosis is crucial for log term planning and future medical decision making.
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The taskforce concluded that a Amyloid PET scan is unnecessary and/or unhelpful for:
Patients with typical Alzheimer’s disease,
Determining the severity of dementia,
Asymptomatic patients with a family history of dementia or positive apolipoprotein E4 status,
Patients who complain of memory loss but have no objective findings,
Testing purely for medico-legal, disability, insurance or employment related issues.
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Find out more:
Click here to find out more about Memory loss, Mild Cognitive Impairment and Alzheimer’s.
Click here to find out more about diagnosing Alzheimer’s.
Links to the Alzheimer’s Association, Alzheimer’s Foundation of America and CDC Healthy Brain Initiative
Neurology Update 