Alzheimer’s Diagnosis: Understanding the Process and Tests

Diagnosing Alzheimer’s disease is a crucial step for individuals experiencing cognitive decline and their families. Being able to articulate your symptoms is an important initial step in this process. Input from close family members or friends can be invaluable in understanding the symptoms and their impact on daily life. Ultimately, a diagnosis of Alzheimer’s disease relies on a combination of memory and thinking skills tests, neurological examinations, and sometimes, advanced blood and imaging tests. These tests help healthcare professionals rule out other conditions and identify biological markers associated with Alzheimer’s.

Historically, a definitive Alzheimer’s diagnosis was only possible post-mortem through microscopic examination of brain tissue to identify plaques and tangles. However, significant advancements now allow for a more confident Alzheimer’s diagnosis during life. This is achieved through a comprehensive evaluation that may include biomarker tests. Biomarkers are crucial as they can detect the presence of plaques and tangles in the living brain. These tests include specialized Positron Emission Tomography (PET) scans and the measurement of amyloid and tau proteins in blood or cerebrospinal fluid (CSF). Recent developments in blood biomarker tests have shown promising accuracy in detecting amyloid presence in the brain.

While biomarker tests were initially primarily used in research settings and clinical trials, their role in clinical Alzheimer’s diagnosis is expanding. Healthcare professionals are increasingly utilizing them alongside traditional assessments to improve diagnostic accuracy and determine the stage of Alzheimer’s disease, whether it’s in the early or later phases.

Comprehensive Testing for Alzheimer’s Diagnosis

A thorough Alzheimer’s diagnosis typically involves a series of tests designed to assess cognitive function, rule out other conditions, and identify Alzheimer’s-specific biomarkers. These tests generally include:

Physical and Neurological Examination

A fundamental part of the Alzheimer’s diagnosis process is a physical and neurological exam conducted by a healthcare professional. This examination assesses various aspects of neurological function, including:

• Reflexes: Checking reflexes helps evaluate the nervous system’s response.
• Muscle Tone and Strength: Assessing muscle tone and strength can identify any motor impairments.
• Gait and Mobility: The ability to rise from a chair and walk assesses balance and coordination.
• Sensory Functions: Testing sight and hearing is important to rule out sensory deficits that might mimic or exacerbate cognitive issues.
• Coordination: Evaluating coordination skills helps identify potential neurological problems.
• Balance: Balance tests are crucial for assessing motor control and stability.

Laboratory Blood Tests

Lab tests, particularly blood tests, play a vital role in Alzheimer’s diagnosis by helping to exclude other treatable conditions that can cause symptoms similar to dementia. These conditions include thyroid disorders and vitamin deficiencies.

Furthermore, cutting-edge blood tests are now available to measure levels of beta-amyloid and tau proteins, which are key biomarkers for Alzheimer’s disease. However, it’s important to note that these advanced blood tests may not be universally accessible and insurance coverage can vary.

Mental Status and Neuropsychological Assessments

Mental status and neuropsychological testing are essential for evaluating cognitive function in individuals suspected of having Alzheimer’s. A brief mental status test is often initially administered to quickly assess memory and thinking skills. More detailed neuropsychological tests provide a comprehensive evaluation of various cognitive domains, such as memory, attention, language, and executive functions. These detailed assessments offer a baseline for comparison against individuals of similar age and education, aiding in diagnosis and providing a benchmark for tracking symptom progression over time.

Brain Imaging Techniques

Brain imaging is a critical component of Alzheimer’s diagnosis, serving two primary purposes: ruling out other structural brain abnormalities and detecting Alzheimer’s-specific changes.

Structural Brain Imaging

Structural imaging techniques like Magnetic Resonance Imaging (MRI) and Computerized Tomography (CT) scans visualize the brain’s structure.

• Magnetic Resonance Imaging (MRI): MRI utilizes radio waves and a strong magnetic field to create detailed images of the brain. In Alzheimer’s diagnosis, MRI can reveal shrinkage in brain regions associated with the disease, such as the hippocampus. Importantly, MRI is also effective in ruling out other conditions that can mimic dementia symptoms, like brain tumors, strokes, or hydrocephalus. MRI is generally preferred over CT scans for dementia evaluation and is often used before starting certain Alzheimer’s medications and during treatment to monitor for potential side effects.

• Computerized Tomography (CT): CT scans use X-ray technology to generate cross-sectional images of the brain. While less detailed than MRI for soft tissue, CT scans are valuable for quickly ruling out tumors, strokes, and head injuries as causes of dementia-like symptoms.

Functional and Molecular Brain Imaging

Functional and molecular imaging techniques, primarily Positron Emission Tomography (PET) scans, provide insights into brain activity and pathology at a molecular level.

• Fluorodeoxyglucose PET (FDG PET) Imaging: FDG PET scans measure brain metabolism by tracking glucose utilization. In Alzheimer’s disease, FDG PET scans can reveal patterns of reduced glucose metabolism in specific brain regions, reflecting neuronal dysfunction. These patterns help differentiate Alzheimer’s from other dementia types.

• Amyloid PET Imaging: Amyloid PET scans use radioactive tracers that bind to amyloid plaques in the brain, allowing for the visualization and quantification of amyloid buildup. While primarily used in research, amyloid PET imaging can be clinically useful in cases with atypical presentations or very early-onset dementia to confirm the presence of Alzheimer’s pathology.

• Tau PET Imaging: Tau PET scans are a newer advancement, utilizing tracers that bind to neurofibrillary tangles, another hallmark of Alzheimer’s disease. Tau PET imaging provides a direct measure of tangle pathology and is increasingly used in research and specialized clinical settings to assess disease severity and progression.

In some instances, particularly when symptoms progress rapidly or in younger individuals, a lumbar puncture may be performed to analyze cerebrospinal fluid (CSF). CSF analysis can measure amyloid and tau protein levels, providing further diagnostic information.

The Future of Alzheimer’s Diagnostic Tests

Biomarker tests represent a significant advancement in Alzheimer’s diagnosis, enabling the detection of biological signs of the disease in the living brain. These tests, when used in conjunction with other diagnostic tools, enhance the accuracy of Alzheimer’s diagnosis after symptoms emerge. Research is ongoing to explore the potential of biomarker tests for pre-symptomatic Alzheimer’s detection. However, current clinical application focuses on individuals exhibiting symptoms. Access to biomarker tests can vary based on location and healthcare resources.

Genetic testing for Alzheimer’s is generally not recommended for everyone. However, it may be considered for individuals with a strong family history of early-onset Alzheimer’s disease. Genetic counseling is crucial to discuss the potential risks and benefits before pursuing genetic testing.

Seeking Expert Care

Accurate and timely Alzheimer’s diagnosis is essential for appropriate care planning and management. Consulting with experienced healthcare professionals is paramount for navigating the diagnostic process and accessing the latest advancements in Alzheimer’s disease assessment.

Request an appointment

More Information

Symptoms & causes
Doctors & departments

References

1. Jankovic J, et al., eds. Alzheimer disease and other dementias. In: Bradley and Daroff’s Neurology in Clinical Practice. 8th ed. Elsevier; 2022.
2. Alzheimer’s disease fact sheet. National Institute on Aging. https://www.nia.nih.gov/health/alzheimers-disease-fact-sheet. Accessed Aug. 23, 2024.
3. Livingston G, et al. Dementia prevention, intervention and care: 2024 report of the Lancet standing Commission. Lancet. 2024; doi:10.1016/S0140-6736(24)01296-0.
4. Chen L, et al. Plasma tau proteins for the diagnosis of mild cognitive impairment and Alzheimer’s disease: A systematic review and meta-analysis. Frontiers in Aging Neuroscience. 2022; doi:10.3389/fnagi.2022.942629.
5. Dementia. World Health Organization. https://www.who.int/news-room/fact-sheets/detail/dementia. Accessed Aug. 23, 2024.
6. Alzheimer’s disease and related dementias. Centers for Disease Control and Prevention. https://www.cdc.gov/aging/aginginfo/alzheimers.htm. Accessed Aug. 23, 2024.
7. What is dementia? Symptoms, types, and diagnosis. National Institute on Aging. https://www.nia.nih.gov/health/diagnosing-dementia. Accessed Aug. 23, 2024.
8. How biomarkers help diagnose dementia. National Institute on Aging. https://www.nia.nih.gov/health/biomarkers-dementia-detection-and-research. Accessed Aug. 23, 2024.
9. Middle-stage caregiving. Alzheimer’s Association. https://www.alz.org/help-support/caregiving/stages-behaviors/middle-stage. Accessed Aug. 23, 2024.
10. Kellerman RD, et al. Alzheimer’s disease. In: Conn’s Current Therapy 2024. Elsevier; 2024.
11. Ferri FF. Alzheimer disease. In: Ferri’s Clinical Advisor 2025. Elsevier; 2025.
12. Early-stage caregiving. Alzheimer’s Association. https://www.alz.org/help-support/caregiving/stages-behaviors/early-stage. Accessed Aug. 23, 2024.
13. Alzheimer’s disease at a glance. National Center for Complementary and Integrative Health. https://nccih.nih.gov/health/alzheimer/ataglance. Accessed Aug. 23, 2024.
14. Budson AE, et al. Memory Loss, Alzheimer’s Disease, and Dementia. 3rd ed. Elsevier; 2022.
15. Care in the late stages of Alzheimer’s disease. National Institute on Aging. https://www.nia.nih.gov/health/coping-late-stage-alzheimers-disease. Accessed Aug. 23, 2024.
16. Graff-Radford J, et al. New insights into atypical Alzheimer’s disease in the era of biomarkers. The Lancet. Neurology. 2021; doi:10.1016/S1474-4422(20)30440-3.
17. Naureen Z, et al. Dietary supplements in neurological diseases and brain aging. Journal of Preventve Medicine and Hygience. 2022; doi:10.15167/2421-4248/jpmh2022.63.2S3.2759.
18. Is Alzheimer’s genetic? Alzheimer’s Association. https://www.alz.org/alzheimers-dementia/what-is-alzheimers/causes-and-risk-factors/genetics. Accessed Aug. 23, 2024.
19. Nimmagadda R. Allscripts EPSi. Mayo Clinic. July 17, 2024.
20. Alzheimer’s disease research centers. National Institute on Aging. https://www.nia.nih.gov/health/alzheimers-disease-research-centers#minnesota. Accessed Aug. 23, 2024.
21. About the Alzheimer’s Consortium. Arizona Alzheimer’s Consortium. https://azalz.org/about/#institutes. Accessed Aug. 23, 2024.
22. Lewis JE, et al. The effects of twenty-one nutrients and phytonutrients on cognitive function: A narrative review. Journal of Clinical and Translational Research. 2021; doi:10.15167/2421-4248/jpmh2022.63.2S3.2759.
23. Home safety. Alzheimer’s Association. https://www.alz.org/help-support/caregiving/safety/home-safety. Accessed Aug. 27, 2024.
24. Argyriou S, et al. Beyond memory impairment: The complex phenotypic landscape of Alzheimer’s disease. Trends in Molecular Medicine. 2024; doi:10.1016/j.molmed.2024.04.016.
25. Grant WB, et al. Diet’s role in modifying risk of Alzheimer’s disease: History and present understanding. Journal of Alzheimer’s Disease. 2023; doi:10.3233/JAD-230418.
26. Wolk DA, et al. Clinical features and diagnosis of Alzheimer disease. https://www.uptodate.com/contents/search. Accessed Aug. 30, 2024.
27. Jack Jr. CR, et al. Revised criteria for diagnosis and staging of Alzheimer’s disease: Alzheimer’s Association Workgroup. Alzheimer’s & Dementia. 2024; doi:10.1002/alz.13859.
28. 2024 Alzheimer’s disease facts and figures. Alzheimer’s Association. https://www.alz.org/alzheimers-dementia/facts-figures. Accessed Aug. 26, 2024.
29. Rosenberg A, et al. Multidomain interventions to prevent cognitive impairment, Alzheimer’s disease and dementia: From FINGER to World-Wide FINGERS. Journal of Prevention of Alzheimer’s Disease. 2020; doi:10.14283/jpad.2019.41.
30. Huang L, et al. Mediterranean-dietary approaches to stop hypertension intervention for neurodegenerative delay (MIND) diet and cognitive function and its decline: A prospective study and meta-analysis of cohort studies. The American Journal of Clinical Nutrition. 2023; doi:10.1016/j.ajcnut.2023.04.025.
31. Fortea J, et al. APOE4 homozygozity represents a distinct genetic form of Alzheimer’s disease. Nature Medicine. 2024; doi:10.1038/s41591-024-02931-w.
32. Ashton NJ, et al. Diagnostic accuracy of a plasma phosphorylated tau 217 immunoassay for Alzheimer disease pathology. JAMA Neurology. 2024; doi:10.1001/jamaneurol.2023.5319.
33. Palmqvist S, et al. Blood biomarkers to detect Alzheimer disease in primary care and secondary care. JAMA. 2024; doi:10.1001/jama.2024.13855.
34. Leqembi (approval letter). Biologic License Application 761269. U.S. Food and Drug Administration. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=761269. Accessed Sept. 5, 2024.
35. Liu E, et al. Updates in Alzheimer’s disease: From basic research to diagnosis and therapies. Translational Neurodegeneration. 2024; doi:10.1186/s40035-024-00432-x.
36. Shi M, et al. Impact of anti-amyloid-β monoclonal antibodies on the pathology and clinical profile of Alzheimer’s disease: A focus on aducanumab and lecanemab. Frontiers in Aging and Neuroscience. 2022; doi:10.3389/fnagi.2022.870517.
37. Lecanemab injection. Facts & Comparisons eAnswers. https://fco.factsandcomparisons.com. Accessed Sept. 6, 2024.
38. Kisunla (approval letter). Biologic License Application 761248. U.S. Food and Drug Administration. https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=761248. Accessed Sept. 6, 2024.
39. Donanemab injection. Facts & Comparisons eAnswers. https://fco.factsandcomparisons.com. Accessed Sept. 6, 2024.
40. Kang C. Donanemab: First approval. Drugs. 2024; doi:10.1007/s40265-024-02087-4.
41. Serafin P, et al. Air pollution: A silent key driver of dementia. Biomedicines. 2023; doi:10.3390/biomedicines11051477.