Diagnosis

An important part of diagnosing Alzheimer's disease includes being able to explain your symptoms, as well as perspective from a close family member or friend about symptoms and their impact on daily life. Additionally, a diagnosis of Alzheimer's disease is based on tests your doctor administers to assess memory and thinking skills.

Laboratory and imaging tests can rule out other potential causes or help the doctor better identify the disease causing dementia symptoms.

But Alzheimer's disease is only diagnosed with complete certainty after death, when microscopic examination of the brain reveals the characteristic plaques and tangles.

Tests

A diagnostic work-up would likely include the following tests:

Physical and neurological exam

Your doctor will perform a physical exam and likely assess overall neurological health by testing the following:

• Reflexes
• Muscle tone and strength
• Ability to get up from a chair and walk across the room
• Sense of sight and hearing
• Coordination
• Balance

Lab tests

Blood tests may help your doctor rule out other potential causes of memory loss and confusion, such as a thyroid disorder or vitamin deficiencies.

Mental status and neuropsychological testing

Your doctor may give you a brief mental status test to assess memory and other thinking skills. Longer forms of neuropsychological testing may provide additional details about mental function compared with people of a similar age and education level. These tests can help establish a diagnosis and serve as a starting point to track the progression of symptoms in the future.

Brain imaging

Images of the brain are now used chiefly to pinpoint visible abnormalities related to conditions other than Alzheimer's disease — such as strokes, trauma or tumors — that may cause cognitive change. New imaging applications — currently used primarily in major medical centers or in clinical trials — may enable doctors to detect specific brain changes caused by Alzheimer's.

Imaging of brain structures include the following:

• Magnetic resonance imaging (MRI). MRI uses radio waves and a strong magnetic field to produce detailed images of the brain. While they may show brain shrinkage of brain regions associated with Alzheimer's disease, MRI scans also rule out other conditions. An MRI is generally preferred to a CT scan for the evaluation of dementia.
• Computerized tomography (CT). A CT scan, a specialized X-ray technology, produces cross-sectional images (slices) of your brain. It's usually used to rule out tumors, strokes and head injuries.

Imaging of disease processes can be performed with positron emission tomography (PET). During a PET scan, a low-level radioactive tracer is injected into the blood to reveal a particular feature in the brain. PET imaging may include the following:

• Fluorodeoxyglucose (FDG) PET scans show areas of the brain in which nutrients are poorly metabolized. Identifying patterns of degeneration — areas of low metabolism — can help distinguish between Alzheimer's disease and other types of dementia.
• Amyloid PET imaging can measure the burden of amyloid deposits in the brain. This imaging is primarily used in research but may be used if a person has unusual or very early onset of dementia symptoms.
• Tau PET imaging, which measures the burden of neurofibrillary tangles in the brain, is generally used in the research setting.

In special circumstances, such as rapidly progressive dementia, dementia with atypical features or early-onset dementia, other tests may be used to measure abnormal beta-amyloid and tau in the cerebrospinal fluid.

Future diagnostic tests

Researchers are working to develop tests that can measure biological signs of disease processes in the brain.

These tests, including blood tests, may improve the accuracy of diagnoses and enable earlier diagnosis before the onset of symptoms. A blood test for Plasma Aβ is currently available and recently received certification in the U.S. by the Centers for Medicare & Medicaid Services to allow distribution on the market.

Genetic testing generally isn't recommended for a routine Alzheimer's disease evaluation. The exception is people who have a family history of early-onset Alzheimer's disease. Meeting with a genetic counselor to discuss the risks and benefits of genetic testing is recommended before undergoing any tests.