Dementia test: Image shows sticky amyloid plaques in the brain of an Alzheimer's patient.
Credit: Wikimedia
NEW YORK: A test that can confirm or rule out Alzheimer's disease at an early stage has been shown effective by U.S. pathologists.
"With this test, we can reliably detect and track the progression of Alzheimer's disease," said lead researcher Leslie Shaw with the University of Pennsylvania's Alzheimer's Disease Neuroimaging Initiative in Philadelphia.
Common dementia
Alzheimer's disease (AD), the most common form of dementia, is a progressive and fatal brain disease that is characterised by sticky beta-amyloid plaques, which build up between brain cells, and also fibre-like proteins called tau tangles.
According to Alzheimer's Australia, a national advocacy group, about half a million Australians currently suffer from the disease.
Yet, despite its prevalence, there has been no definitive test for the early stages of the disease. Patients are typically diagnosed through a battery of tests from neurologists and psychologists. Only an autopsy can confirm the presence of amyloid plaques and tau tangles in the brain, however.
The new test is detailed in the journal Annals of Neurology. It measures the cerebral-spinal fluid (CSF) concentration of two biochemicals associated with the disease — amyloid beta42 peptide and tau protein.
Rigorous trials
While it has been known for some time that concentrations of these markers might indicate the presence of the disease, the new study is the first time that an Alzheimer's test has undergone rigorous trials in multiple laboratories, including patients who were later confirmed to have had Alzheimer's with an autopsy.
The study measured CSF samples from 400 patients with mild cognitive impairment, 200 with early-stage AD, and 200 with normal brain function. The researchers also tested CSF samples taken from 56 patients prior to their death, and on whom autopsies later confirmed the presence of the disease.
The researchers found that patients with mild cognitive impairment or AD had much larger concentrations of tau and decreased concentrations of amyloid beta42, as compared to the healthy patients.
Overall, the test was 87 per cent accurate, and was able to both indicate which patients with mild cognitive impairment would progress to AD, and which patients did not have AD.
