From the Guidelines
Blood tests for suspected dementia should include a comprehensive panel to identify potentially reversible causes of cognitive impairment, and emerging blood biomarker tests for amyloid pathology may be useful in clinical practice, as recommended by the Global CEO Initiative on Alzheimer's Disease 1. When dementia is suspected, doctors typically order a comprehensive panel including:
- Complete blood count
- Comprehensive metabolic panel
- Thyroid function tests (TSH, free T4)
- Vitamin B12 levels
- Folate levels
- Sometimes syphilis serology These tests help identify potentially reversible causes of cognitive impairment such as:
- Vitamin deficiencies
- Thyroid disorders
- Infections
- Metabolic abnormalities Additional specialized tests might include:
- Homocysteine levels
- Inflammatory markers like ESR or CRP
- In some cases, genetic testing for specific mutations associated with familial forms of dementia Blood tests for biomarkers such as beta-amyloid and tau proteins are emerging, and the Global CEO Initiative on Alzheimer's Disease recommends minimum acceptable performance of blood biomarker tests for clinical use 1. It's essential to understand that these tests primarily rule out other conditions rather than confirm dementia, which ultimately requires:
- Clinical evaluation
- Cognitive testing
- Brain imaging
- Sometimes cerebrospinal fluid analysis for a comprehensive diagnosis Early testing is crucial as identifying and treating reversible causes can prevent further cognitive decline. The use of blood biomarker tests for amyloid pathology may become an essential component of the routine assessment of people who present for evaluation of cognitive impairment, especially with the increasing availability of disease-modifying treatments for Alzheimer's disease 1.
From the Research
Blood Tests for Suspected Dementia
- The initial laboratory evaluation for suspected dementia includes tests for thyroid-stimulating hormone and vitamin B12 levels 2.
- Other tests such as complete blood count and electrolyte, glucose, calcium, and thyroid levels are also recommended as part of the core investigations 3.
- The Canadian Consensus Conference on the Assessment of Dementia (CCCAD) guidelines suggest that family physicians should use clinical judgment in ordering laboratory investigations 3.
- Tests for syphilis and computed tomography scan of the head may be considered when the clinical situation warrants 3.
- A baseline measurement of cognitive function should be obtained, and the Mini-Mental State Examination is the most commonly used instrument to document cognitive impairment 2.
Additional Testing
- Structural neuroimaging with noncontrast computed tomography or magnetic resonance imaging is also recommended 2.
- Neuropsychologic testing can help determine the extent of cognitive impairment, but it is not recommended on a routine basis 2.
- Further testing should be guided by the history and physical examination, and may include age-appropriate cancer screenings, basic metabolic panel, liver function tests, and other tests as needed 4.