Alzheimer’s Disease: Diagnosis

Diagnosis of Alzheimer's Disease

To diagnose Alzheimer's disease, your doctor performs a comprehensive evaluation. No single test can definitively diagnose Alzheimer's. The diagnostic process includes medical history, physical and neurological examination, cognitive tests, and imaging methods.

Alzheimer's diagnosis is primarily a "diagnosis of exclusion"; meaning it is made after ruling out other causes of dementia such as vitamin deficiencies, thyroid disorders, brain tumors, and medication side effects. It is also necessary to demonstrate that symptoms are progressive and affecting daily life.

Your doctor first takes a detailed medical history. Questions are asked about when symptoms began, how they have progressed, family history, current medications, and past medical problems. Family members or close friends are included in the evaluation because the patient may not be aware of their symptoms or may minimize them.

A physical and neurological examination is performed. Reflexes, muscle strength, coordination, balance, sensory functions, and vision are tested. Physical problems that could affect brain function (such as stroke or Parkinson's disease) are evaluated.

Cognitive and Neuropsychological Tests

• Mini-Mental State Examination (MMSE). This is the most widely used brief cognitive screening test. It consists of 30 questions and evaluates memory, attention, language, calculation, and visual-spatial skills. The maximum score is 30; scores of 24-30 indicate normal cognition, 18-23 indicate mild impairment, and 0-17 indicate severe cognitive impairment. The MMSE is quick and easy to administer but can be influenced by education level.
• Montreal Cognitive Assessment (MoCA). Similar to the MMSE but more sensitive, the MoCA is better at detecting mild cognitive impairment. It also evaluates executive functions and abstract thinking skills. The maximum score is 30; a score of 26 or above is considered normal.
• Clock Drawing Test. The patient is asked to draw a clock face and indicate a specific time. It evaluates visual-spatial skills, planning, and executive functions. Simple but useful for detecting cognitive impairment.
• Detailed neuropsychological test battery. These are comprehensive tests administered by a specialist neuropsychologist. Memory (short- and long-term), attention, language, visual-spatial skills, and executive functions are evaluated in detail. These tests can take several hours but provide a detailed cognitive profile and help distinguish Alzheimer's from other types of dementia.
• Functional assessment. Questionnaires assessing activities of daily living (ADL) are administered. Basic ADLs (eating, dressing, bathing) and instrumental ADLs (shopping, managing finances, taking medications) are evaluated. Functional impairment is required for a dementia diagnosis.

Laboratory Tests

• Blood tests. These are performed to rule out treatable causes of dementia. A complete blood count, metabolic panel, thyroid function tests (TSH), vitamin B12 and folic acid levels, and electrolytes are measured. Kidney and liver function are checked. A syphilis test (VDRL) and sometimes an HIV test may also be performed.
• Cerebrospinal fluid (CSF) analysis. A CSF sample is obtained via lumbar puncture (spinal tap). Low levels of beta-amyloid 42 and high levels of total tau and phosphorylated tau in the CSF support an Alzheimer's diagnosis. However, this test is not routine and is generally performed for atypical cases or research purposes.
• Alzheimer's blood biomarkers (New). New tests that measure beta-amyloid and tau proteins in the blood are being developed. These tests can enable non-invasive early diagnosis. The FDA has approved some blood tests (such as PrecivityAD), but they are not yet in widespread use.

Brain Imaging

• Magnetic Resonance Imaging (MRI). MRI shows brain structures in detail. In Alzheimer's, shrinkage (atrophy) is seen in the hippocampus and other brain regions. MRI also rules out other causes of dementia such as stroke, tumor, and hydrocephalus. Structural MRI is the standard imaging method in Alzheimer's diagnosis.
• Computed Tomography (CT). Similar to MRI, CT shows brain structure but with less soft tissue detail. CT is faster and less expensive. It detects acute conditions such as stroke, bleeding, and tumors. Brain atrophy can be seen in Alzheimer's, but MRI is preferred.
• Positron Emission Tomography (PET). PET shows brain metabolism and protein accumulation. It is used to detect amyloid plaques and tau tangles in the brain, providing valuable information for early and accurate diagnosis.

Genetic Tests

• APOE genotyping. This test checks for the presence of APOE-e4. However, it is not routinely recommended because carrying APOE-e4 does not guarantee Alzheimer's, and not carrying it does not eliminate risk. It may be considered alongside genetic counseling.
• Early-onset Alzheimer's gene tests. In cases with onset before age 65 and a strong family history, APP, PSEN1, and PSEN2 gene mutations can be tested. These mutations follow an autosomal dominant inheritance pattern (50% transmission risk). Genetic counseling is essential.

Preparing for Your Appointment

Seeing a doctor with suspected or diagnosed Alzheimer's disease can be stressful. Going prepared helps facilitate the diagnosis and treatment process.

What you can do:

• Note symptoms in detail (When did they start? How have they progressed? Give examples).
• Bring a family member or close friend (they can describe symptoms the patient may not be aware of).
• Prepare a medication list (prescription, over-the-counter, vitamins, herbal products).
• Compile family history (Is there Alzheimer's, dementia, or memory problems in the family?).
• Bring previous medical records if available (blood tests, brain imaging, past cognitive test results).
• Write your questions in advance.

Questions you can ask your doctor:

• Are these symptoms Alzheimer's disease or another condition?
• What tests are needed for a definitive diagnosis?
• What stage is the disease at?
• What are the treatment options?
• What are the side effects of the medications?
• How will the disease progress?
• How often is follow-up needed?
• Is it safe to drive?
• What should we do for legal and financial planning?
• What support resources are available (support groups, care services)?
• Can we participate in clinical trials?

Your doctor may ask you:

• When did the memory problems begin?
• How have the symptoms progressed? Are they worsening rapidly?
• Is there difficulty with daily activities? (Finances, shopping, medications, dressing)
• Are there personality or behavioral changes?
• Has the person gotten lost or had trouble finding their way?
• Is there a family history of dementia or Alzheimer's?
• Are there other health problems?
• What medications are you taking?
• Is there any alcohol or substance use?
• Are there signs of depression or anxiety?