How Can A Blood Test Diagnose Alzheimer’s Disease?

Conclusively diagnosing Alzheimer’s disease was previously a costly process that was not always widely available, but developments in pharmacy blood tests mean that more people will be diagnosed earlier, helping to slow its progression.

Following the recent approval in the United States of a blood test for use in patients showing symptoms over the age of 40, hopes have been raised for a simple, easy-to-use and widely available blood test that could diagnose a disease with complicated early symptoms.

How does a dementia blood test work? Why does it matter? And how could it change the field of phlebotomy as a whole?

How Is Alzheimer’s Disease Typically Diagnosed?

At present, there is no single test that can confirm or deny dementia, although considerable research is being undertaken to try and fix this.

Instead, the traditional diagnostic pathway relies on a range of assessments, tests and examinations of a person’s medical history.

These include:

• A discussion with a GP regarding symptoms

• A referral to a specialist to examine one’s medical history in further detail

• Cognitive assessments to demonstrate issues with memory, concentration, language or spatial awareness

• Blood or urine tests

• Brain scans such as computed tomography or magnetic resonance imaging

• Additional scans such as PET scans

The goal is partly to positively identify certain biomarkers and behaviours associated with dementia, and to rule out some potential alternative causes of symptoms sometimes linked with dementia.

How Could Blood Tests Be Used To Diagnose Alzheimer’s Disease?

At present, blood tests are typically used to rule out other conditions or identify treatable conditions which can exacerbate dementia or present with dementia-like symptoms.

Cognition is particularly strongly affected by your blood and organ function, and in the early stages of symptomatic dementia, issues with cognition and memory could be linked to:

• Anaemia

• Salt processing issues caused by kidney problems

• Elevated liver enzymes, often but not always related to alcohol intake

• Calcium levels

• Hypothyroidism, which can be reversed by proper treatment

• Vitamin B12 deficiency

• Folate deficiency

• Vitamin D deficiency

• Diabetes

• Autoimmune disorders

• Cardiovascular disorders

• Sexually transmitted infections

The presence of biomarkers for any of these conditions could potentially rule out dementia or suggest a comorbidity, but if none of these is present, it could suggest that it is worth further examination.

The problem is that the tests above can be relatively uncommon, forcing people to decide between going on a waiting list or paying considerable amounts of money to get certain scans done privately.

Is it possible for a blood test to track any signs of dementia itself?

Can Blood Tests Detect Dementia Itself?

It is possible, and tests have been used in laboratory settings to determine a positive diagnosis. However, tailored blood tests would be needed for each type of dementia, making a widespread screening campaign much harder than it is for cancer.

The two key biomarkers found in a brain affected by Alzheimer’s disease are amyloid and tau protein, both of which can be detected in blood as the body tries to flush them from building up in the brain, and they either leak into the blood or end up in the blood via spinal fluid.

If a test could be developed that could combine multiple of these, it is possible for blood tests to detect dementia on a wider scale, but at present they are not quite available.