Blood Test Identifies Alzheimer’s With 90% Accuracy

As highly accurate blood tests for Alzheimer’s disease are moving closer to use in physician’s offices, new research suggests that they may revolutionize the accuracy of diagnosis and provide a cleaner, quicker path to research participation and treatment, according to data reported today at the Alzheimer’s Association International Conference® (AAIC®) 2024, in Philadelphia and online.

Dementia is often underdiagnosed — and if it is diagnosed by a clinician, many people nonetheless are unaware or uninformed of their diagnosis, according to the 2024 Alzheimer’s Disease Facts and Figures report. Blood tests for Alzheimer’s are demonstrating in research that they could significantly improve a clinician’s accuracy and confidence, provide greater accessibility and a platform for enhanced communication.

Blood tests that show the most promise for identifying Alzheimer’s-related changes in the brain assess phosphorylated tau (p-tau) protein, an Alzheimer’s biomarker that can build up before patients show signs of cognitive impairment. Increases in the specific marker p-tau217 over time correlate with worsening cognition and brain atrophy. The p-tau217 test also predicts the likelihood of amyloid plaques in the brain, which are another biomarker for Alzheimer’s and the target for recently approved treatments.

“Blood tests, once they (a) are confirmed in large populations to be more than 90% accurate and (b) become more widely available, show promise for improving, and possibly redefining, the clinical trial recruitment process and the diagnostic work-up for Alzheimer’s,” said Maria C. Carrillo, Ph.D., Alzheimer’s Association chief science officer and medical affairs lead. “While at this time doctors in primary and secondary care should use a combination of cognitive and blood or other biomarker testing to diagnose Alzheimer's, blood tests have the potential to increase the accuracy of early diagnoses and maximize the opportunity to access Alzheimer’s treatments as early as possible for better outcomes.”

When considering use of a blood test, the Alzheimer’s Association Appropriate Use Recommendations for Blood Biomarkers in Alzheimer’s Disease should be carefully followed. To help guide health care professionals in incorporating blood tests for Alzheimer’s in their clinical practice, the Association has convened a panel of clinical and subject-matter experts and is leading the preparation of clinical practice guidelines for the use of blood biomarkers in Alzheimer’s, which will be previewed at AAIC 2024.

Blood Test Can Improve Diagnosis Among Primary Care and Alzheimer’s Disease Specialists

A large study, reported for the first time at AAIC 2024, shows that blood tests can do a better job of accurately detecting Alzheimer's than both primary care doctors and specialists who were using traditional diagnostic methods.

In the study, 1,213 patients were tested with the PrecivityAD2 test (known as “APS2”). It uses a combination of (1) plasma phosphorylated-tau217 to not-phosphorylated-tau217 ratio (known as %p-tau217) and (2) the ratio of two types of amyloid (Aβ42/Aβ40), and it significantly outperformed clinicians in this study.

• Among 698 patients seen at memory clinics, APS2 was around 90% accurate at identifying Alzheimer’s disease while specialists were 73% accurate.
• Among 515 patients seen in primary care, APS2 was also around 90% accurate; primary care physicians were 63% accurate at identifying Alzheimer’s.

Researchers observed that the APS2 test was highly accurate even in patients with comorbidities, such as kidney disease, which are common in older patients seen by primary care physicians.

“Notably, these were the results of blood samples that have been shipped bi-weekly for analysis from primary care units, which is similar to routine clinical practice,” said lead author Sebastian Palmqvist, M.D., Ph.D., at Lund University, Lund, Sweden. “These results were especially impressive considering that older populations in primary care often have medical conditions that can influence or vary the concentrations of p-tau217.”

“We see this as a major step towards global clinical implementation of an Alzheimer’s blood test,” said senior author Oskar Hansson, M.D., Ph.D., also at Lund University. “It highlights the need for Alzheimer’s biomarkers in making a correct diagnosis more of the time. The next steps include establishing clear guidelines for how an Alzheimer’s blood test can be used in clinical practice, preferably by implementing these tests first in specialist care and then in primary care. This work is currently ongoing.”

Reference: Palmqvist S, Tideman P, Mattsson-Carlgren N, et al. Blood biomarkers to detect Alzheimer's disease in primary care and secondary care. JAMA. 2024. doi: 10.1001/jama.2024.13855

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