From the Guidelines
The most effective approach to testing for Alzheimer's disease is through the use of blood biomarker (BBM) tests, specifically those measuring the plasma Aβ42/Aβ40 ratio or phosphorylated tau species like p-tau217, due to their high accuracy and acceptability to patients. When considering the diagnosis of Alzheimer's disease, it's crucial to prioritize methods that offer a balance between accuracy, patient comfort, and practicality in a clinical setting 1.
Key Considerations in Alzheimer's Testing
- Accuracy and Acceptability: BBM tests have shown promising results, with assays of the plasma Aβ42/Aβ40 ratio having receiver operating characteristic area under the curve (AUC) values of 0.70–0.85, and assays for p-tau217 or its ratio to non-phosphorylated tau achieving AUCs of 0.92–0.98 1.
- Clinical Practicality: Unlike amyloid PET, which is highly informative but limited by cost and the need for specialized personnel, and CSF tests, which require lumbar puncture and may have limitations in terms of patient willingness and clinician comfort, BBM tests offer a more accessible and scalable option 1.
- Comprehensive Diagnostic Approach: While BBM tests are highly promising, a comprehensive diagnosis of Alzheimer's disease should still involve cognitive assessments, medical history, physical examinations, and potentially other diagnostic tools like MRI or PET scans to rule out other causes of cognitive impairment 1.
Evolution of Diagnostic Recommendations
The field of Alzheimer's disease diagnosis is evolving, with ongoing research into biomarkers and diagnostic frameworks like the ATN research framework, which emphasizes the importance of amyloid and tau pathology 1. As novel fluid biomarkers are developed and studied, the approach to diagnosing Alzheimer's disease is likely to become even more refined, potentially incorporating new BBM tests that more accurately reflect tau pathology.
Conclusion on Best Practice
Given the current state of evidence, utilizing BBM tests as part of a comprehensive diagnostic approach offers the best balance of accuracy, patient acceptability, and clinical practicality for diagnosing Alzheimer's disease 1. This approach aligns with the goal of improving morbidity, mortality, and quality of life outcomes by facilitating earlier and more accurate diagnoses, which can in turn guide appropriate treatment and management strategies.
From the Research
Testing for Alzheimer's Disease
The best testing for Alzheimer's disease involves a combination of cognitive screening tests, laboratory assessments, and imaging studies. Some of the commonly used cognitive screening tests include:
- Montreal Cognitive Assessment (MoCA) 2, 3, 4, 5
- Mini-Mental State Examination (MMSE) 2, 3, 4
- Cognitive Abilities Screening Instrument (CASI) 5
- History-based Artificial Intelligence-Show Chwan Assessment of Cognition (HAI-SAC) 5
Comparison of Cognitive Screening Tests
Studies have compared the accuracy of MoCA and MMSE in detecting mild cognitive impairment and Alzheimer's disease. The results suggest that:
- MoCA has better performance than MMSE in screening dementia associated with Alzheimer's disease 2, 3, 4
- MoCA has higher diagnostic accuracy and sensitivity than MMSE in detecting mild cognitive impairment and Alzheimer's disease 3, 4
- HAI-SAC is a novel screening test that has shown promising results in differentiating between cognitively unimpaired individuals, patients with mild cognitive impairment, and patients with dementia of Alzheimer's type 5
Diagnostic Criteria and Assessment
The diagnosis of Alzheimer's disease involves a stepwise process that includes: