Alzheimer disease (AD) is the most common form of dementia. It is characterized by debilitating and progressive episodic memory loss, difficulty with language and decision making, and (in advanced stages) loss of motor control, incontinence, and mutism. Nearly 44 million people around the world have been diagnosed with AD, and it is most prevalent in Western Europe, with North America trailing closely behind. In the U.S., nearly six million Americans have AD and two-thirds of those affected are women.

Early diagnosis is necessary for patients to seek appropriate medical treatments and support services in a timely manner. Diagnosis before cognitive function is greatly impacted affords patients the opportunity to make long-term legal, financial and healthcare decisions for themselves. It also allows for patients with AD to be appropriately placed in long-term care facilities earlier, which reduces healthcare costs associated with delayed placement.

What You Need to Know:

Large quantities of beta-amyloid (Aβ) deposits are found in the senile plaques of the AD brain. Preliminary research has demonstrated promising results for a β-amyloid blood test which was used to screen patients for AD and has potential application in primary care. Two cohorts were included in this multicenter study. The first cohort was comprised of 842 participants; 513 were cognitively intact, 265 had mild cognitive impairment, and 64 had AD. The second (validation) cohort included 237 participants; 34 were cognitively intact, 109 had mild cognitive impairment, and 94 had AD. Immunoassay was used to measure plasma β-amyloid 42 and β-amyloid 40 to calculate cerebral β-amyloid status in each stage of AD. Diagnostic accuracy improved when APOE genotype was also analyzed.

The study concluded that β-amyloid 42 and β-amyloid 40 ratio blood tests, with APOE genotype may be used in primary care pre-screening for AD and in AD clinical trials to decrease associated expenses and quantity of positron emission tomography (PET) scans and lumbar punctures ordered. 

Read more about Alzheimer Disease:

Adams and Victor’s Principles of Neurology, 11e: Chapter 38. Degenerative Diseases of the Nervous System > Diseases Characterized Mainly by Progressive Dementia

Harrison’s Principles of Internal Medicine, 20e: Chapter 423. Alzheimer’s Disease

Current Diagnosis and Treatment: Psychiatry, 3e: Chapter 3. Psychiatric Genetics > Alzheimer Disease

The Color Atlas and Synopsis of Family Medicine, 3e: Chapter 243. Dementia