A recently published review in Alzheimer’s & Dementia looked at how well blood-based biomarker tests can help detect Alzheimer’s disease pathology in people with cognitive impairment seen in specialist care settings (i.e. memory clinics). The review aims to provide the scientific foundation for the US Alzheimer’s Association’s new clinical guidelines on using these tests in practice. The researchers searched for studies published between 2019 and 2024 that tested how accurately certain blood markers, such as phosphorylated tau and amyloid beta, can identify Alzheimer’s disease compared to established methods like spinal fluid tests, brain scans or autopsy results. The review found that blood markers such as p-tau181, p-tau217, %p-tau217, p-tau231, and Aβ42/Aβ40 are associated with Alzheimer’s pathology. However, the accuracy of markers in blood varied considerably between tests and platforms, with sensitivity ranging from 49.3% to 91.4% and specificity from 61.5% to 96.7%.
The performance of these tests depends heavily on the type of assay used, which means results should always be interpreted alongside a full clinical assessment. Many tests are not reliable enough when using just one cutoff point, therefore a two-threshold approach is recommended to improve accuracy. Combining markers, such as p-tau217 with Aβ42/Aβ40, can improve accuracy but did not eliminate the need for confirmatory clinical assessment and imaging (e.g. PET scans). The article brings together evidence from 31 different blood tests and supports new guidelines on how they can be used in diagnosing Alzheimer’s disease in memory clinics. As research moves forward, ongoing evaluation of new tests and combinations will be key to improving accuracy and keeping guidelines up to date.