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  • Kayla Hui

Alzheimer’s Blood Test

Approximately 5.8 million people in the United States 65 and older have Alzheimer’s disease. Alzheimer’s is the most common progressive neurodegenerative disorder that results in brain atrophy and loss of brain cells. It is also one of the most common causes of dementia, with 60 to 70 percent of dementia patients having Alzheimer’s. Dementia is an individual having a continuous decline in thinking, behavioral, and social skills. This results in a severe decrease in a person's ability to function without additional help.

Alzheimer’s disease results in persistent memory loss which could result in getting lost in familiar places or forgetting the names of family members and other critical objects. Other than memory loss Alzheimer's causes difficulty concentrating and thinking. This severely impairs an individual’s ability to multitask. Furthermore, Alzheimer’s impairs people from making reasonable decisions and judgments in everyday situations. Although there are medications that may temporarily improve or slow the progression of these symptoms, there is no treatment to alter the disease process. For these reasons, it is dangerous for a patient to be left alone. Therefore it has become essential for Alzheimer’s to be detected before the symptoms worsen and possibly place the individuals in further danger.

However, many cases of Alzheimer's are left undetected. It is essential to prevent the further danger of a person to detect Alzheimer’s disease before the initial symptoms occur. For the past century, a definitive Alzheimer’s diagnosis could only be achieved through autopsy. Even now, Alzheimer’s can be diagnosed through brain imaging and spinal fluids before the initial symptoms. However, these tests are invasive and expensive, limiting the number of people diagnosed and eventually given care for Alzheimer’s disease. The Alzheimer’s blood test serves to present a more accessible and efficient method to detect Alzheimer's disease.

In the fall of 2020, an Alzheimer’s blood test was developed in St. Louis Missouri by C2N Diagnostics, and it became available to most of the US for a routine lab test. This test was named PrecivityAD and it uses mass spectrometry, an analytic technique used to measure the mass-to-charge ratio of one or more molecules, to detect specific types of beta-amyloid. Most notably PrecivityAD detects apolipoprotein E which is known to influence Alzheimer’s disease risk.

Beta-amyloid is a protein that is the primary component of plaques, brain lesions, that are characteristic of Alzheimer’s. Beta-amyloid is formed from the breakdown of a larger protein, known as the amyloid precursor protein. The beta-amyloid then clumps together, resulting in plaque that collects between neurons. As plaque builds up in the brain levels of beta-amyloid decrease in the surrounding fluid, this concept was previously used in spinal fluid tests. PrecivityAD is the beginning of a new generation of assays that could allow for early detection of Alzheimer’s, possibly several decades before the onset of the first symptoms.

PrecivityAD is the first blood test for Alzheimer’s to be cleared for widespread use, it is being regulated by the Clinical Laboratory Improvement Amendments (CLIA) program. The blood test also has received a CE mark as a diagnostic medical device in the European Union. The CE mark indicates that the Alzheimer’s blood test has met safety, health, and environmental protection standards for that region.

However, PrecivityAD only results in a probability score that reflects the likelihood of an amyloid-positive brain scan and is calculated using the person’s age as a factor. For this reason, Precivity is meant for 60 to 91 year-olds with early signs of cognitive impairment and is used to enhance the accuracy of a clinical diagnosis. PrecivityAD is supposed to be used in collaboration in a clinical diagnosis to distinguish Alzheimer’s dementia from memory loss due to other conditions.

Overall Alzheimer’s blood test provides a more accessible version that could in the future help to show who is at risk for Alzheimer’s. PrecivityAD is also a far more affordable version as it is less expensive than a diagnosis through positron-emission tomography (PET) brain imaging or through a sample cerebrospinal fluid (CSF). Also, both these procedures are highly invasive and burdensome. In comparison, a blood test can be collected from people in remote locations or their homes. Although there are still no drugs approved for Alzheimer's, early detection tests could improve treatment by letting patients take measures, plan for their future or participate in clinical trials.

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