Detecting Alzheimer disease is complicated. There are no simple tests. Doctors can perform cognitive function evaluations and order brain imaging. To date, though, definitive diagnosis relies on autopsy examination to determine if a person really had extensive plaques of beta amyloid or tangles of tau in the brain. Brain scans and analyses of cerebrospinal fluid have made it possible to identify this type of dementia before death, but these are not easy or affordable tests.Now, however, one or another blood test for Alzheimer disease may allow for early diagnosis.
Blood Test More Accurate Than Cognitive Assessments:
Researchers reported in JAMA on a blood test that is more accurate than CT scans and much more reliable than cognitive tests (JAMA, July 28, 2024). The blood test uses mass spectrometry to identify a form of tau linked to Alzheimer disease. In the study, the blood test identified people with AD 90% of the time. In comparison, primary care physicians were able to detect 61% of the cases and dementia specialists were 73% accurate. This new blood test could make early diagnosis more feasible.
What Is the Blood Test for Alzheimer Disease?
Researchers previously reported that a blood test might detect signs of neuron degeneration many years before symptoms appear (Nature Medicine, Jan. 21, 2019). The investigators published their findings in Nature Medicine. For this ground-breaking research, they utilized an unusual group of volunteers, including 247 people who had a genetic risk for early-onset Alzheimer disease. Importantly, those who had this particular rare genetic marker were predestined to show symptoms of dementia at approximately the same age as their nearest relatives with the disease. The scientists matched these individuals to family members without the genetic marker. All the subjects gave blood, performed cognitive tests and underwent imaging scans.
A Special Protein Appears in the Blood Test for Alzheimer Disease:
The researchers analyzed the participants’ blood for a protein called neurofilament light chain that is released when brain cells disintegrate. The people with a gene for early Alzheimer disease had higher protein levels when first tested. Moreover, their levels of neurofilament rose steadily over time. The other participants had steady low levels of the protein.
Differences in the protein were detectable sixteen years before the expected onset of symptoms. Rapid increases in neurofilament light chain levels were also linked to brain shrinkage visible on scans. This preliminary test is not yet ready for clinical use, but the authors hope that it will someday allow doctor to diagnose Alzheimer disease when intervention might still make a difference.
Learn More:
This new blood test for Alzheimer disease will be welcome if it actually assists with early diagnosis. Some specialists are already using a variety of tests to determine if someone may be vulnerable to this devastating condition and, most importantly, to treat the factors that contribute to cognitive dysfunction. To learn more, you may wish to listen to our interview with Dr. Dale Bredesen. It is Show 1092: How Can You Overcome Alzheimer Disease?
Another interview of interest is Show 1326: Think Different About Alzheimer Disease with Dr. Donald Weaver.
You may also wish to read about other new tests being developed to detect Alzheimer disease early, including a type of MRI called diffusion tensor imaging. Special retinal imaging called optical coherence tomography angiography also shows promise for early diagnosis of Alzheimer disease.
