On June 28, 2024, the Alzheimer’s Association (AA) published revised criteria for the diagnosis and staging of Alzheimer’s disease (AD), the first update since 2018.
The revised criteria describe a biological process that begins with the onset of neuropathological changes associated with AD, even before observable symptoms are present. As this process progresses, clinical symptoms eventually appear and the disease advances. The criteria categorize AD biomarkers into three broad categories:
Additionally, core biomarkers of AD are subdivided into Core 1 and Core 2:
Core 1 biomarkers become abnormal early in the disease process and directly measure amyloid plaques or phosphorylated tau (p-tau). These include amyloid PET; cerebrospinal fluid (CSF) amyloid beta 42/40 ratio, CSF p-tau181/amyloid beta 42 ratio, and CSF total (t)-tau/amyloid beta 42 ratio; as well as plasma biomarkers like p-tau217. An abnormal Core 1 biomarker result is considered sufficient for diagnosing AD and making clinical decisions related to the disease.
Core 2 biomarkers become abnormal later in the disease process and are more closely related to the onset of symptoms. Core 2 biomarkers include tau PET and certain soluble tau fragments associated with tau proteinopathy (e.g., MTBR-tau243), pT205, and non-phosphorylated mid-region tau fragments. Core 2 biomarkers can be used, in combination with Core 1, to rate the biological severity of the disease and increase confidence that AD is contributing to the patient's symptoms.
The guidelines emphasize that the biological-based diagnosis of AD is intended to assist rather than replace the clinical evaluation of individuals with cognitive impairment.
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