From the Guidelines
When diagnosing dementia, laboratory tests such as thyroid function tests, vitamin B12, homocysteine, complete blood count with differential, complete metabolic panel, erythrocyte sedimentation rate, and C-reactive protein should be requested to rule out reversible causes and identify contributing factors. These tests are essential to identify conditions like electrolyte imbalances, kidney or liver dysfunction, thyroid disorders, vitamin deficiencies, and infections that can cause or worsen cognitive symptoms 1. Some key laboratory tests to consider include:
- Thyroid function tests to assess for thyroid disorders
- Vitamin B12 level to identify vitamin deficiencies
- Complete blood count with differential to evaluate for anemia or other blood disorders
- Complete metabolic panel to assess for electrolyte imbalances, kidney or liver dysfunction
- Erythrocyte sedimentation rate and C-reactive protein to evaluate for inflammatory conditions Additionally, structural brain imaging with MRI (or head CT if MRI is contraindicated) is also recommended to rule out structural abnormalities 1. It is crucial to tailor the laboratory evaluation to the patient's clinical presentation, age, and risk factors, with more extensive testing for younger patients or those with atypical presentations. The goal of these laboratory tests is to exclude treatable conditions that mimic dementia, rather than to diagnose Alzheimer's disease itself 1.
From the Research
Laboratory Tests for Diagnosing Dementia
The following laboratory tests are used to diagnose dementia:
- Blood tests, including complete blood cell count, blood chemistry battery, and thyroid function tests 2
- Cerebrospinal fluid assays, which may be considered in atypical dementia cases 3
- Genetic testing, which may be considered in atypical dementia cases, such as age of onset younger than 65 years, rapid symptom onset, and/or impairment in multiple cognitive domains but not episodic memory 3
- Electroencephalography (EEG), which may be performed as clinically indicated 4
- Computed tomography (CT) or magnetic resonance imaging (MRI), which may be used to rule out treatable causes of dementia or to rule in cerebrovascular disease 4, 5
Core Laboratory Tests
A list of core laboratory tests is recommended for the diagnosis of dementia, including:
- Complete blood cell count
- Blood chemistry battery (especially sodium, calcium, and glucose concentrations)
- Thyroid function tests 2, 5
Selective Use of Diagnostic Tests
Diagnostic tests, such as functional imaging, measurement of biomarkers, and neuropsychologic testing, should be used selectively based on the results of the examination and screening tests 2, 5