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Biomarkers for Alzheimer’s

About 10 million new cases of dementia are diagnosed worldwide every year, of which, 60% to70% are Alzheimer’s Disease (AD), as per the World Health Organisation (WHO). AD is the most common cause of dementia which leads to a gradual decline in memory,thinking, behaviour, and social skills.Hence, it is obvious that the disease needs to be diagnosedearly for effective interventions.

However, it is challenging to diagnose AD in its early stages because it often goes unnoticeduntil symptoms become significant. The gold standard for diagnosis is a pathological analysis ofthe brain tissue of the patient which is invasive and not practical. The other methods areMagnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) scans which areexpensive. Cerebrospinal fluid analysis for molecular biomarkers is another diagnostictechnique that is invasive.

What are biomarkers?

Early diagnosis with biomarkers or biological markers is a less invasive and non-expensive method that is currently feasible. Biomarkers are devices used to evaluate biological markers inbody fluids like blood, saliva, and urine.

In AD, diagnostic biomarkers focus on three pathologic features: abnormal amyloid beta peptide accumulation, abnormally phosphorylated tau-protein, and nonspecificneuronal degeneration. The most extensively evaluated plasma AD biomarkersare the plasma amyloid- (A), especially amyloid beta 42 and amyloid beta 40, and the phosphorylated tau (p-tau)protein at epitopes 181, 217, and 231.

Accumulation of amyloid plaques in the brain is a hallmark of Alzheimer’s dementia. Studieshave shown that certain forms of amyloid beta peptides, such as amyloid beta 42, are elevated in the blood.

What do Indian researchers say about AD biomarkers?

Indian researchers are looking for the imbalance of certain prevalent biomarkers specific toAD, using surface-enhanced Raman spectroscopy (SERS) and nanoparticle probes to classifyblood samples as “healthy”, with mild cognitive impairment (MCI) and dementia.They are veryclose to perfecting the clinical validation of a diagnostic platform, which will enable the earlydetection of AD through a simple and affordable blood test.

The estimated dementia prevalence for adults aged 60+ in India is 7.4%. The average survivalrate of Alzheimer’s is 3 to 9 years. This would translate into a huge burden on the society.Hence, the need of the hour is early diagnosis at a pre-clinical stage. Nevertheless, we are onthe threshold of an exciting era where artificial intelligence and new body fluid-basedbiomarkers, in combination with other risk factors, will provide a novel solution that willrevolutionise the early diagnosis of AD.

Blood-based biomarkers for the diagnosis of Alzheimer’s are all the more important as thenewer interventions with disease-modifying properties like Aducanumab and Lecanemab act attheir best in the early stages of the disease.

(The author is a consultantneurologist and stroke physician.)

(Published 14 October 2023, 23:20 IST)

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