There are four primary categories of tests to determine a diagnosis (or not) of Alzheimer’s disease: cognitive tests, brain imaging, biomarker tests and genetic testing.
COGNITIVE TESTS
Cognitive tests involve a series of assessments to measure and evaluate functions including memory, thinking, problem solving, concentration, language skills and spatial awareness. Doctors use these tests to diagnose the disease, often in combination with one another. The most used cognitive tests are:
- Mini-Mental State Examination (MMSE): This is a widely used, fairly simple screening tool that assesses various functions, including arithmetic ability, memory and orientation.
- Montreal Cognitive Assessment (MoCA): This test is considered more sensitive to detecting mild cognitive impairment than the Mini-Mental State Examination; it evaluates memory, attention level, language and visuospatial skills.
- Clock Drawing Test (CDT): This simple test involves drawing a clock to show specific times to assess visuospatial and executive functions.
- Alzheimer’s Disease Assessment Scale-Cognitive Subscale (ADAS-Cog): The ADAS-Cog is a more detailed and comprehensive assessment tool that includes various tasks for evaluating memory, language, specific skills (praxis) and other cognitive abilities.
- Saint Louis University Mental Status Exam (SLUMS): This screening tool is similar to MoCA and MMSE and provides a broader assessment of cognitive function.
These cognitive tests are readily available and provide tracking of disease progression with repeated administration of the tests.
BRAIN IMAGING
Imaging techniques view areas of the brain that may be affected by the buildup of amyloid plaque bundles and tau tangles. Examples include:
- Magnetic Resonance Imaging, also known as MRI: This is a noninvasive medical imaging technique that provides a detailed view of the structure of the brain and any physical abnormalities. Magnetic resonance imaging can identify the structural changes in the brain caused by progressive cell death and atrophy.
- Positron Emission Tomography, or PET: This medical imaging tool shows the structural details of the brain as well as information about the brain’s activity and how it is working. It requires the injection of a radiotracer into the bloodstream. These radiotracers are specific to different proteins making up the different pathologies, including amyloid and tau, and allow for the identification and assessment of the degree of each pathology.
FLUID BIOMARKER TESTS
Biomarkers are indicators that assess the presence or severity of a disease. For Alzheimer’s disease, very recent scientific advancements have resulted in the creation of separate fluid biomarker tests for the detection of two key proteins found in the brains of those with Alzheimer’s disease: amyloid beta and tau. Each of these now can be measured in cerebrospinal fluid to see whether abnormal, elevated levels of these proteins are present, which can indicate the presence of Alzheimer’s disease pathology in the brain.
A study published in February 2024 demonstrated that a new blood test can diagnose Alzheimer’s disease pathology as accurately as cerebrospinal fluid tests and brain scans, even in patients with mild symptoms. The test also can detect molecular signs of Alzheimer’s disease in the brain before symptoms appear. “The accuracy of this blood test now enables us to diagnose the presence of Alzheimer’s disease pathology with a single blood sample,” said Dr. Randall J. Bateman, co-senior author of the study, the Charles F. and Joanne Knight Distinguished Professor of Neurology at Washington University School of Medicine in St. Louis and a member of the Cure Alzheimer’s Fund Research Leadership Group. He added, “This advance will increase accurate diagnoses for many patients.”
Read more here. To learn more about the blood test, please view this webinar.
GENETIC TESTING
While there are a number of genes associated with Alzheimer’s disease, a genetic test is unlikely to prove definitively if a person will develop the disease. According to the National Institutes of Health, “Genetic tests are not routinely used in clinical settings to diagnose or predict the risk of developing Alzheimer’s or a related dementia. In some cases, if a person has symptoms at an early age with a strong family history of Alzheimer’s, a neurologist or other medical specialist may order a genetic test for various genes, including APP, PSEN1, and PSEN2. Although APOE testing is also available, the results cannot fully predict who will or won’t develop Alzheimer’s. Rather, this type of testing is used primarily in research settings to identify study participants who may have an increased risk of developing Alzheimer’s.”
Please speak with your physician to understand your options for testing and diagnosis.