Objective:

To evaluate a blood test measuring amyloid beta aggregation seeding activity for distinguishing Alzheimer’s disease and mild cognitive impairment from normal cognition and other dementias.

Approach:

• Study Design: Researchers recruited 549 patients at Xuanwu Hospital, assessing a blood test in a discovery group of 120 patients and a validation group of 429 patients.
• Test Methodology: The test utilized protein misfolding cyclic amplification to detect misfolded amyloid beta in plasma, measuring aggregation with a fluorescent dye.
• Sample Testing: Each sample was tested twice, with laboratory investigators blinded to patients' clinical information.

Key Findings:

• The assay distinguished Alzheimer’s disease from normal cognition with an area under the curve of 0.93.
• For mild cognitive impairment due to Alzheimer’s disease, the area under the curve was 0.92.
• The plasma assay outperformed cerebrospinal fluid biomarkers in distinguishing Alzheimer’s disease from non-Alzheimer’s dementia.

Interpretation:

Higher plasma seeding activity correlated with poorer cognitive performance and greater dementia severity.

Limitations:

• Diagnoses were based on clinical criteria without neuropathologic confirmation.
• The study did not compare the assay with established plasma biomarkers such as phosphorylated tau 217.
• The cross-sectional design limited assessment of the test’s predictive ability for disease progression.
• Validation in populations outside of China is necessary.

Conclusion:

The blood test shows promise as a biomarker for Alzheimer’s disease and related conditions, but further validation is needed.

Sources:

• Chinese Medical Journal