Can you get a blood test for dementia?

A recent study advertised by the Alzheimer’s Society revealed that 56% of people delay seeking a dementia diagnosis for a year or longer after they first suspect that they have dementia symptoms. Dementia holds is one of the most feared health conditions in the UK. This fear is perhaps understandable, considering nearly two-thirds of respondents (62%) believe a diagnosis signifies the end of their quality of life.

Many people wonder if it’s possible to get dementia blood tests like you can for infectious diseases. In short, there is no definitive test for dementia because dementia is a collection of symptoms. However, some biomarkers are correlated with certain types of dementia. Let’s explore these biomarkers and then explain how dementia is diagnosed in the UK.

Types of Biomarkers and Tests

Biomarkers are measurable indicators of what’s happening in the body. These can be found in the blood, other body fluids, organs, and tissues. For dementia, several types of biomarkers help in detection and diagnosis.

Brain Imaging

Brain imaging allows doctors and scientists to look at the various factors that will help diagnose dementia. These scans are crucial for identifying sources of damage to the brain, such as tumours or strokes.

Computerised Tomography (CT) 

A CT scan uses X-rays to create images of the brain. It can show shrinkage of brain areas, a common indicator for many types of dementia, and other sources of disease, such as infections or blood clots. CT scans help compare the size of brain areas to previous scans or expected sizes for a person's age and size.

Magnetic Resonance Imaging (MRI)

MRI utilises magnetic fields and radio waves to provide comprehensive images of brain structures. It can show brain atrophy and provide a detailed image of brain blood vessels. MRI scans are useful in ruling out other reasons for memory changes, such as bleeding or fluid build-up.

Positron Emission Tomography (PET)

A PET brain scan uses a radioactive substance to measure the specific activities or molecules in the brain. They reveal regions of normal and abnormal chemical activity. Types of PET scans include amyloid PET, tau PET, and fluorodeoxyglucose (FDG) PET, each measuring different brain components linked to dementia.

• Amyloid PET Scans: These scans measure irregular deposits of a protein called beta-amyloid, which is correlated with Alzheimer's disease. Higher levels of beta-amyloid indicate the presence of amyloid plaques, a hallmark of Alzheimer's. However, it's important to note that some people with amyloid plaques may never develop symptoms of Alzheimer's.
• Tau PET Scans: These scans detect the irregular accumulation of tau protein within nerve cells, which is another feature of Alzheimer's and other dementias. Elevated tau levels are associated with neurofibrillary tangles that disrupt brain cell function.
• Fluorodeoxyglucose (FDG) PET scans: FDG PET scans measure glucose metabolism in the brain, providing insights into brain activity levels. Decreased glucose use in specific brain areas can indicate neurodegenerative diseases like frontotemporal dementia. These scans help distinguish between different types of dementia based on metabolic patterns.

Cerebrospinal Fluid Biomarkers (CSF)

CSF surrounds the brain and spinal cord, providing protection and essential nutrients. Measuring changes in CSF biomarkers, like beta-amyloid 42, tau, and phospho-tau, helps diagnose Alzheimer's disease and other dementias. A lumbar puncture, or spinal tap, is performed to obtain CSF.

• Beta-Amyloid 42: A specific form of beta-amyloid, a protein fragment that accumulates to form plaques in the brain, linked to Alzheimer's disease. Low levels in CSF suggest that beta-amyloid is being deposited in the brain, which is a sign of Alzheimer’s.
• Tau and Phospho-Tau: Tau is a protein that helps maintain the structure of brain cells. Phospho-tau is a modified form of tau that forms tangles inside brain cells in Alzheimer's and other dementias. High levels of tau and phospho-tau in CSF indicate the presence of these tangles, which are harmful to brain function and are correlated with Alzheimer's disease and other neurodegenerative conditions.

Blood Tests

Blood tests are becoming more accurate in identifying dementia biomarkers. For instance, levels of beta-amyloid can now be measured, though these tests are primarily only available in research settings. Despite advancements, dementia blood tests alone cannot provide a definitive diagnosis.

• Beta-Amyloid: A protein that can form clumps or plaques in the brain, commonly found in Alzheimer's disease. These plaques disrupt communication between brain cells. Elevated levels in blood can suggest Alzheimer's disease.
• Other Proteins: Ongoing research is identifying additional proteins that may indicate different types of dementia.

Genetic Testing

Genetic tests analyse DNA to determine a person's genetic makeup. Mutations in genes can lead to diseases like Alzheimer's. While not routinely used for diagnosis, genetic tests might be ordered if there's a strong family history of dementia. Genetic counselling accompanies these tests to discuss risks, benefits, and limitations.

• Mutations in MAPT and GRN Genes: Associated with frontotemporal dementia.

How Dementia is Diagnosed in the UK

If you're worried about memory loss or think a loved one might have dementia, it’s best to see a GP. Early diagnosis provides the best possible chance to prepare for the future with proper support from healthcare professionals, family, and friends.

GP Appointment

A GP will ask about symptoms, medical history, and how everyday activities are managed. Bringing someone who knows the person well can help describe any changes or problems noticed. Memory problems can have other causes, such as depression, anxiety, infections, or side effects of medicines. The GP will do a physical exam and may organise tests like a complete blood count and urine test.

Referral to a Specialist

Dementia can be difficult to diagnose, especially with mild symptoms. If other causes are ruled out, the GP may refer the person to a specialist, such as a psychiatrist, geriatrician, or neurologist. Specialists often work in memory clinics and may conduct further tests, including brain scans like CT, MRI, or PET scans.

Formal Diagnosis

The specialist will consider all test results and symptoms to make a diagnosis. While it’s a feared condition, an accurate and early diagnosis can lead to better management and support. The doctor should discuss the type of dementia, its progression, treatment options, and support services available. Written information about dementia and ongoing assessments should be provided to help manage the condition effectively.

Conclusion

While there isn’t a simple blood test for dementia, various biomarkers and diagnostic tests help in the detection and diagnosis of different types of dementia, including vascular dementia and frontotemporal dementia. In the UK, a combination of physical exams, memory tests, brain imaging, and specialist referrals contribute to an accurate diagnosis.

At Tiggo Care, we understand the complexities of dementia diagnosis and the challenges it brings to families. Our personalised dementia care service aims to maximise quality of life and provide comprehensive support for those living with dementia. Whether it's assisting with medication routines, meal preparation, or escorting to social events, our dedicated care assistants are here to help. Contact Tiggo Care today to learn more about our tailored dementia care services and how we can support your loved one’s needs.