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A blood test for Alzheimer's
At present, diagnosing Alzheimer’s consists of examining an individual's clinical history and undergoing memory testing and brain scans, a process that can be lengthy and invasive and does not always yield a definitive answer. But an international study—the largest of its kind—might now offer a noninvasive and more accurate way to diagnose the neurodegenerative disorder for better treatment, and to aid clinicians in differentiating between other neurodegenerative diseases.
The study included researchers from Lancaster University, the University of Central Lancashire (UCLan), the University of Manchester and the Federal University of Rio Grande do Norte, Brazil. The work was published in the Proceedings of the National Academy of Sciences (PNAS), in a paper titled “Differential diagnosis of Alzheimer’s disease using spectrochemical analysis of blood.”
Prof. Francis Martin, Biosciences theme lead at UCLan and principal investigator of the study, said: “We have an aging population, meaning that the incidence and prevalence of Alzheimer’s is increasing, as is the need for accurate diagnosis. The ability to identify different neurodegenerative diseases through the analysis of blood offers a faster and accurate way of establishing the most effective treatment plan as well as disease monitoring.”
The team's work consisted of applying sensor-based technology with a diamond core for analysis, also known as attenuated total reflection FTIR spectroscopy. Passing light through the diamond and studying how it interacted with blood plasma enabled the scientists to identify specific chemical bonds within the blood, and they used that data to compare blood samples from individuals with Alzheimer’s disease and other neurodegenerative diseases with samples from healthy controls. Blood samples from a total of 549 individuals—347 of whom had various neurodegenerative diseases and 202 of whom were age-matched healthy controls—were processed for the study. All plasma samples and supporting clinical and genetic information were provided by Prof. David Allsop of Lancaster University and Prof. David Mann of the University of Manchester, who have worked together for years in pursuit of diagnostic markers for neurodegenerative diseases within blood plasma.
As explained in the PNAS paper, “Vibrational spectroscopy is an ideal technique for analysis of biofluids, as it provides a 'spectral fingerprint' of all of the molecules present within a biological sample, thus generating a holistic picture of the sample’s status.” Their approach allowed them to identify Alzheimer’s disease with 70 percent sensitivity and specificity. After incorporating apolipoprotein ε4 genotype (APOE ε4) information, that increased to 72 percent sensitivity and 77 percent specificity when individuals lacked ε4 alleles, and 86 percent sensitivity and specificity when they had one or two ε4 alleles. Early cases of Alzheimer’s disease were detected with 80 percent sensitivity and 74 percent specificity, and the team was able to determine between Alzheimer’s disease and dementia with Lewy bodies with 90 percent sensitivity and specificity.
Allsop noted in a press release that, “A particularly exciting aspect of the study was the ability to distinguish accurately between Alzheimer’s disease and Lewy body dementia, which are conditions that both result in dementia and can be difficult to separate from each other based on clinical information and symptoms. By reduction of misdiagnosed cases and administration of appropriate treatment, many people could benefit from this type of blood test in the future.”
It's thought that this method could also help clinicians identify and monitor early signs of mild cognitive impairment, which could aid in the earlier detection of Alzheimer’s onset (and that of other neurodegenerative disorders) and potentially early treatment to slow disease progression.
“For those suffering with Alzheimer’s disease, the damage is already well advanced once conventionally diagnosed, but this new method offers a potentially effective early screening tool when patients are only demonstrating signs of mild cognitive impairment,” said Martin. “This is a potentially significant breakthrough for the prevention of different debilitating and chronic neurological diseases.”
In other recent Alzheimer’s disease-related news from the University of Manchester, a team of researchers found that it's possible to use certain measurements of brain activity to predict Alzheimer’s in patients with mild memory problems. The study consisted of 44 healthy control individuals, 40 individuals with Alzheimer’s disease and 94 individuals with mild cognitive impairment (MCI) from the Alzheimer’s Disease Neuroimaging Initiative. Many individuals with MCI end up developing Alzheimer’s disease, though not all do. The team, led by Karl Herholz, Professor of Clinical Neuroscience at the Wolfson Molecular Imaging Centre, analyzed cognitive test results as well as the results of PET scans, and found that the PET scans performed at the beginning of the study showed greater impairment in people with MCI who eventually developed Alzheimer’s than in those who did not. These scans were also found to be better for predicting which individuals would develop Alzheimer’s disease than cognitive tests, with the ability to detect alterations in brain function over a shorter period of time.