What laboratory tests and evaluations are recommended for a dementia workup?

Recommended Laboratory Tests for Dementia Workup

A standard dementia workup should include complete blood count, comprehensive metabolic panel, thyroid function tests, vitamin B12 and folate levels, as these tests can identify the most common reversible causes of cognitive impairment. 1, 2

Core Laboratory Tests (First-Line)

• Complete blood count (CBC) - To evaluate for anemia, infection, or other hematologic abnormalities
• Comprehensive metabolic panel - To assess electrolytes, renal and liver function
• Thyroid stimulating hormone (TSH) - To rule out hypothyroidism
• Vitamin B12 and folate levels - To identify nutritional deficiencies
• Homocysteine levels - Additional marker for B12/folate deficiency
• HbA1c - To evaluate for diabetes
• Lipid profile - To assess vascular risk factors

Additional Tests (Second-Line, Based on Clinical Suspicion)

• Erythrocyte sedimentation rate (ESR) - For inflammatory conditions
• HIV antibody testing - Particularly in high-risk populations or atypical presentations
• Rapid plasma reagin (RPR) or FTA-ABS - To screen for syphilis
• Lyme disease antibody testing - In endemic areas or with suggestive history
• Ammonia levels - If hepatic encephalopathy is suspected
• Antinuclear antibody (ANA) - For autoimmune conditions
• Urinalysis and urine culture - To rule out urinary tract infection

Advanced Testing (For Specialty Evaluation)

• Cerebrospinal fluid (CSF) analysis - For AD biomarkers (Aβ42, tau, phospho-tau) when diagnostic uncertainty remains after initial workup 1, 2
• Autoimmune panels - In cases of rapid progression or atypical features
• Methylmalonic acid (MMA) - More sensitive marker for B12 deficiency
• Paraneoplastic antibody panels - In cases with rapid progression or unusual features

Imaging Studies

• Brain MRI (preferred) or CT - To assess for structural causes, vascular disease, and patterns of atrophy 1, 2
• FDG-PET - For cases with diagnostic uncertainty after initial workup 1
• Amyloid PET - For select cases when AD diagnosis remains uncertain 1

Cognitive Assessment Tools

• Montreal Cognitive Assessment (MoCA) - More sensitive for mild cognitive impairment 1
• Mini-Mental State Examination (MMSE) - For tracking cognitive change over time 1
• Clock Drawing Test - Simple screening tool 1

Implementation Algorithm

1. Initial presentation with cognitive complaints:

   • Perform core laboratory tests (CBC, metabolic panel, TSH, B12, folate)
   • Conduct cognitive screening (MoCA or MMSE)
   • Obtain corroborative history from reliable informant 1

2. If initial tests are normal but cognitive concerns persist:

   • Proceed with brain MRI
   • Consider second-line laboratory tests based on clinical suspicion
   • Refer to specialty care if diagnosis remains unclear

3. For continued diagnostic uncertainty in specialty care:

   • Consider CSF analysis for AD biomarkers 1
   • Consider FDG-PET 1
   • Consider advanced cognitive testing

Common Pitfalls to Avoid

• Failing to obtain collateral history - Essential for accurate assessment of cognitive decline 1, 2
• Overlooking reversible causes - Complete laboratory workup is critical as studies show 1-10% of dementia cases may have potentially reversible components 3, 4
• Premature diagnosis - Diagnosis should never be made solely based on cognitive screening tests 1
• Excessive testing - A selective approach based on clinical findings can reduce costs by 65-75% compared to ordering all possible tests 5
• Ignoring multiple pathologies - Many patients have mixed pathologies (e.g., Alzheimer's with vascular components) 6

This approach ensures identification of potentially reversible causes while maintaining cost-effectiveness and avoiding unnecessary testing. The laboratory evaluation should be tailored based on the patient's age, risk factors, and clinical presentation, with more extensive testing reserved for atypical presentations or when initial workup is inconclusive.