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Alzheimer’s disease affects an estimated 416 million people globally, or 22% of all people aged 50 and above.1 This debilitating neurological disease affects the patient’s memory, thinking and reasoning, eventually making it difficult for them to complete the simplest tasks.2
The good news is that recent advances in biomarker research are enabling earlier, more accurate diagnosis of Alzheimer’s disease, which, together with advances in treatment options, is likely to improve patient outcomes.3
Common Diagnostic Tests for Alzheimer's Disease
The journey to receiving an Alzheimer's diagnosis is different for each patient and is often dependent on the healthcare systems available to them.
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The importance of early Alzheimer's detection: Alzheimer’s can cause pathological changes in the brain years or even decades before symptoms like memory loss and confusion start to show. An early and accurate diagnosis is crucial for treatment planning and for helping the patient, their family and their healthcare practitioners to make informed decisions about their care and support.3 Better testing = earlier diagnosis = improved patient outcomes |
Typical diagnostic tests for Alzheimer's include the following:3
Cognitive assessments
Standardized tests are available to assess memory, thinking and problem-solving skills. These tests help to gauge the patient’s cognitive function.3
- Challenges and limitations: Cognitive assessments can't be used to definitively diagnose Alzheimer's because other conditions, or even normal aging, can cause similar symptoms. Cognitive tests usually only happen in the advanced stages of Alzheimer’s.3
Imaging tests
Magnetic resonance imaging (MRI) and computed tomography (CT) scans might be used to rule out a differential diagnosis such as a stroke or tumor, but they can’t definitively diagnose Alzheimer’s.3
More advanced PET scans, which have radioligand reporters that bind a molecular target, can be used to detect Alzheimer’s.3
- Challenges and limitations: Imaging tests like positron emission tomography (PET) scans are expensive and require special equipment which may not be available in some healthcare facilities.3
Measurement of soluble biomarkers
Soluble biomarkers for Alzheimer’s are present in cerebrospinal fluid (CSF) and blood. This is because CSF is in direct contact with brain tissue, and it means that it can be tested for the presence of certain proteins associated with changes happening in the brain.3
Currently, the best biomarkers for Alzheimer’s include:3
- Aβ42 (amyloid-beta plaques)
- phosphorylated (p)-tau (tau tangles)
- total (t)-tau
- neurofilament light (NfL)
- glial fibrillary acidic protein (GFAP).
These biomarkers reflect different pathologic aspects of the disease, like neurodegeneration (indicated by NfL) and neuroinflammation (indicated by GFAP).3
- Challenges and limitations: CSF sampling requires a painful, invasive and expensive lumbar puncture procedure.3
*Please visit the below links if you'd like to read more on:
- Tau and Amyloid-beta proteins as key diagnostic tools
- Neurofilament light (NfL): Valuable tool for diagnostics and maintenance of neurological disease
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The significance of soluble biomarkers: Previously, diagnosing Alzheimer’s disease during life was based purely on clinical symptoms, with definitive diagnosis only being possible during autopsy after death. The discovery of these CSF biomarkers in the late 20th century marked a turning point in Alzheimer’s diagnosis, offering new hope for earlier and more specific diagnoses.3 The use of soluble biomarkers has been included in the new consensus diagnostic criteria for Alzheimer’s disease, proposed by the National Institute on Aging and the Alzheimer’s Association (NIA-AA).3 |
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The Future of Alzheimer's Testing: Blood Tests
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The newest NIA-AA update, expected in 2024, includes recommendations for blood-based detection of soluble biomarkers.4 |
Opportunities and challenges
Blood-based testing has great potential to improve the diagnostic process. For example, a blood test is being researched whereby Alzheimer’s could be detected by measuring the levels of brain-derived Aβ, p-tau, NfL and GFAP in plasma, so a patient could be tested without the need for a lumbar puncture or an expensive PET scan.3
“With the advent of highly sensitive immunoassays, the development of blood-based biomarkers has accelerated; mounting evidence now supports their clinical usefulness and reliability in both prodromal and dementia stages of the disease.” - Clinical Chemistry and Laboratory Medicine (CCLM)5
*Please visit the below link if you'd like to read more on:
- Blood-based biomarkers in Alzheimer’s disease – moving towards a new era of diagnostics
However, a successful Alzheimer’s blood test needs to be extremely sensitive and specific, because the biomarkers can be hard to detect. This is because:3
- The biomarkers are often present in low levels.
- Changes in the brain may be masked by similar proteins expressed by the peripheral body.
- Blood is a more complex protein mixture than CSF, and a matrix effect (caused by IgGs or albumin for example) can more easily occur in assay setups.
Developing a high-quality Alzheimer’s blood test
“The future of diagnostics lies in less invasive and accessible methods, and the emergence of blood tests is a game-changer.” - Emilia Galli, R&D Manager, Medix Biochemica3
Antibodies are the workhorses of many diagnostic tests, specifically binding to target molecules like disease markers. But an in vitro diagnostic (IVD) test is only as strong as its weakest component – any raw ingredient may cause errors and inconsistencies, leading to missed or incorrect diagnoses.3
The good news is that Medix Biochemica excels in providing high-performing monoclonal antibodies (mAbs) with:3
- High specificity: We study the cross reactivities to relevant proteins and indicate the results in our product specification sheets.
- High sensitivity: We study the performance and sensitivity of mAb pairs and recommend the most suitable pairs in our product specification sheets.
- Low batch-to-batch variation: We ensure consistency across different batches, ensuring reliable test results over time.
To analyze blood-derived markers which are present in very low levels, high-sesnsitivity and specificity mAbs must be combined with extra-sensitive assay techniques.3
Techniques like digital ELISA or single molecule array (Simoa) assays boast astonishing sensitivity, detecting tiny amounts of biomarkers with between 100 and 1000x higher sensitivity compared to traditional immunoassays. Another technique, immunoprecipitation mass spectrometry (IP-MS), combines precise protein capture with mass spectrometry analysis, ensuring highly specific detection of the target molecules.3
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Exciting novel blood test development: *Please visit the below link if you'd like to read more on: |
Alzheimer's and Genetics
There’s no single genetic cause for Alzheimer’s disease. A person can carry more than one genetic variant or group of variants that can increase their risk of Alzheimer’s.7
When IVD blood tests for Alzheimer’s become more widely available, earlier detection will become easier, meaning that people carrying the genetic variants that put them at risk can be tested long before they begin to experience symptoms.8
How Medix Biochemica empowers IVD testers
Medix Biochemica provides IVD manufacturers with the raw materials they need to develop high-quality assays to improve patient care. By partnering with us, our clients gain access to cutting-edge antibody technology and expertise.3
We offer mAbs, control antigens, base matrices and patient samples for test development. We’re known for our high quality, consistency and ability to produce materials on a large scale. The rapid advancements in biomarker research present exciting opportunities to expand our development pipeline and address unmet medical needs in neurodegenerative diseases.3
Extensive research is being done to improve the diagnostic process and pave the way to a brighter future for Alzheimer’s patients – and Medix Biochemica is excited to play our part in improving the lives of those affected by, and at risk for, Alzheimer’s disease.
References:
- Gustavsson A, Norton N, Fast T, et al. Global estimates on the number of persons across the Alzheimer’s disease continuum. Alzheimer’s & Dementia. 2023;19(2):658-670. doi:10.1002/alz.12694.
- Alzheimer’s disease fact sheet. National Institute on Aging. Accessed March 4, 2024. https://www.nia.nih.gov/health/alzheimers-and-dementia/alzheimers-disease-fact-sheet.
- Expert opinion. Email from Emilia Galli, R&D Manager, Medix Biochemica. February 29, 2024.
- Revised criteria for diagnosis and staging of Alzheimer's disease: Alzheimer’s Association Workgroup. Accessed March 5, 2024. https://aaic.alz.org/diagnostic-criteria.asp.
- Arslan B, Zetterberg H, Ashton NJ. Blood-based biomarkers in Alzheimer’s disease – moving towards a new era of diagnostics. CCLM. January 23, 2024. doi:10.1515/cclm-2023-1434.
- Amin R, Dey BK, Alam F, et al. Cutting-edge approach for Alzheimer’s disease detection in the early stages: an overview. Int J Surg. 2023;109(3):582-583. doi:10.1097/JS9.0000000000000177.
- Alzheimer’s disease genetics fact sheet. National Institute on Aging. Accessed March 5, 2024. https://www.nia.nih.gov/health/genetics-and-family-history/alzheimers-disease-genetics-fact-sheet.
- Expert opinion. Interview with Emilia Galli, R&D Manager, Medix Biochemica. March 1, 2024.
