July 17, 2021 -- International experts are proposing that Alzheimer’s disease should be diagnosed using biomarkers – traits of a person’s health obtained by taking blood, fluid, and tissue samples – rather than testing memory and observing symptoms.
Under the proposed guidelines, medical providers would use a numerical staging system and give patients a ranking from 0 to 6 that reflects the state of their condition, much like the staging system used in cancer diagnoses, Reuters reported. The ranking would be based on the detection of biomarkers and cognitive changes.
“Care has to evolve with the science,” Maria C. Carrillo, PhD, Alzheimer’s Association chief science officer, said in a news release. “Our understanding of Alzheimer’s disease has advanced, in particular our understanding of biomarkers, and this needs to be reflected in how we describe and diagnose the disease.”
One of the core principles of the project is that “Alzheimer’s disease (AD) should be defined biologically, not based on a clinical syndrome(s).”
The new diagnostic measures are expected to speed up Alzheimer’s diagnoses, allowing patients to make informed decisions earlier, the news release said. Doctors should also be able to determine earlier whether a patient has Alzheimer’s or a different condition with similar symptoms.
The new guidelines would replace guidelines adopted in 2018. The change is prompted by major advances in testing for biomarkers, which are sometimes called molecular markers and signature molecules.
Biomarkers can be obtained many ways, including blood tests and brain scans. Blood testing allows doctors to better detect the buildup of beta amyloid and tau proteins in the brain, which are signs a person has or is developing Alzheimer’s disease.
A draft of the new guidelines was presented Sunday at the Alzheimer’s Association International Conference in Amsterdam. The draft guidelines are open for expert review and comment and may be revised after comments.
Reuters said the staging system includes four biological stages that are ranked a, b, c, and d.
For instance, a person ranked in Stage 1a would show no symptoms of having Alzheimer’s but have abnormal biomarkers. In Stage 2, a patient would have abnormal biomarkers and subtle changes in behavior and cognition. Stage 3 is very much like the current pre-symptomatic stage called mild cognitive impairment. Stages 4, 5, and 6 are equivalent to mild, moderate, and severe dementia.
Stage 0 would be for people who have genes that indicate they are likely to develop Alzheimer's, such as those with Down Syndrome.
One of the potential complications of the new staging system is that a person could be diagnosed as having stage 1 Alzheimer’s based on a blood test alone, while showing no signs of memory loss, CNN reported.
Clifford Jack, MD, a neuroradiologist at the Mayo Clinic and a co-author of the guidelines, said some Alzheimer’s experts are not happy about that possibility. “This is a big controversy in the field,” he told CNN.