New scheme proposed for diagnosing Alzheimer's disease

2022 08 01 18 21 3281 Brain Amyloid Plaque Neuron 400

Experts have drafted new diagnostic criteria for Alzheimer's disease to reflect recent advances in the field, according to a July 16 presentation delivered at an international conference.

The proposal is a revamp of the 2018 National Institute on Aging-Alzheimer's Association Alzheimer's research framework and was presented at the 2023 Alzheimer's Association International Conference in Amsterdam.

"Care has to evolve with the science," Maria Carrillo, PhD, chief science officer of the Alzheimer's Association, 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."

The update comes in response to several recent developments, according to the authors, led by Clifford Jack, MD, of the Mayo Clinic in Rochester, MN. Primarily, since 2018, several targeted therapies have received approval to treat the disease, and prescriptions for these drugs will require confirmation of disease pathology prior to use.

Under the proposal, patients would receive a score of 1 to 7 based on the presence of abnormal disease biomarkers and clinical changes in cognition. These scores would be based largely on brain PET imaging for beta-amyloid plaque or tau neurofibrillary tangles (hallmarks of the disease), as well as on tests for cerebral spinal fluid or blood biomarkers such as phosphorylated tau (p-tau).

Specific to biological staging with PET, the authors are proposing the following staging scheme:

  • Stage A (initial): Abnormal amyloid PET with no uptake on tau PET (A+T-)
  • Stage B (early): Abnormal amyloid PET plus tau PET uptake that is restricted to the brain's medial temporal areas (A+TMTL+)
  • Stage C (intermediate): Abnormal amyloid PET plus tau PET uptake in the moderate standardized uptake value ratio (SUVR) range on a neocortical region of interest (ROI) (A+TMOD+)
  • Stage D (advanced): Abnormal amyloid PET plus tau PET uptake in the high SUVR range in the same neocortical ROI (A+THIGH+)

The new framework also includes a Stage 0 for people who are genetically susceptible to Alzheimer's disease yet who show no significant symptoms, according to the proposal.

"The present document has progressed from a framework for research, to criteria for diagnosis and staging that are intended for clinical use as well as research," the authors noted.

The authors noted that the focus of the document is on criteria for diagnosing and staging Alzheimer's disease. A discussion on the use of PET scans or other biomarkers for monitoring the effects of new treatments is beyond the scope of this work, they added.

The proposal will be available for public comment for 30 days on the Alzheimer's Association AAIC website.

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