A common theme emerging from Alzheimer’s disease research is the need for early diagnosis of the subtle signs and symptoms of Alzheimer’s and other types of dementia in the Pre-Clinical or Mild Cognitive Impairment (MCI) phase of disease progression:
Types of Early Diagnosis Tests for Alzheimer’s Disease
(1) Cognitive and Memory Tests
There are a large number of well validated tools to screen for memory loss and other types of cognitive impairment. Several of these cognitive tests are now available on computers and tablet devices – download a full list of computerized cognitive screening tests.
Readers can also view and download several paper-based cognitive screening tests. Be sure to carefully read the screening test instructions.
If you concerned about the possibility of memory loss or cognitive impairment in a friend or loved one, use the free Memory Loss Checklist to determine the possibility of serious memory problems.
(2) Brain Imaging Tests
Positron Emission Tomography (PET) imaging tests and Magnetic Resonance Imaging (MRI) tests can provide valuable information on whether a person has brain biomarker signs of Alzheimer’s or other types of dementia.
PET imaging tests can identify amyloid beta deposits in the brain by using imaging agents that are introduced into the brain through the bloodstream. These imaging agents bind to amyloid beta plaques in the brain, allowing for a sensitive and generally accurate measure of amyloid beta “load” or “burden” in the patient’s brain.
Structural MRI imaging is used to measure the size and volume of various brain regions. Two regions in particular, the hippocampus and entorhinal cortex, are known to atrophy and shrink during the progression of Alzheimer’s disease.
(3) Genetic Tests
More than 200 individual genes are possibly involved in Alzheimer’s disease progression. The best established gene data available for late onset (after age 65) Alzheimer’s is the APOE gene, specifically the e4 variant (APOE E4). The E4 variant appears to increase the risk of Alzheimer’s, especially for people who have two copies of E4. The APOE E2 variant, carried by about 20% of the population, seems to provide some protection against developing Alzheimer’s.
However, current research also indicates that lifestyle and health factors such as smoking, obesity, and hypertension have a large influence on the risk of developing Alzheimer’s or other types of dementia:
(4) Cerebrospinal Fluid (CSF) Tests
Cerebrospinal fluid analysis of amyloid beta and tau protein levels can provide an accurate diagnosis of Alzheimer’s, and also act as a predictive tool for conversion probability from MCI to Alzheimer’s. CSF tests require an invasive procedure known as a lumbar puncture.
(4) (Future) Blood Serum Tests
Blood based biomarker screening for Alzheimer’s disease hold great promise for a routine, cost effective testing method, but there is much work to be done to turn this type of test into reality for primary care & general practice settings.
A number of serious roadblocks remain before a blood plasma screening instrument is ready for general clinical use. Top among these issues are a lack of standards for blood collection, use of different assay platforms, and lack of training and reporting mechanisms for clinical environments. Read this article for further detail on blood screening for Alzheimer’s and dementia.