Initial Laboratory Evaluation for Cognitive Impairment
Order complete blood counts, serum chemistries, and urinalysis as part of the initial evaluation for this patient with progressive cognitive decline. 1
Rationale for Laboratory Testing
The American Academy of Neurology guidelines explicitly recommend screening for reversible causes of dementia as part of the initial diagnostic workup 1. This approach is critical because:
- Screening for B12 deficiency and hypothyroidism should be performed as these are treatable causes of cognitive impairment that can mimic or exacerbate dementia 1
- Depression screening should be performed to identify a potentially reversible contributor to cognitive symptoms 1
- Complete blood counts and serum chemistries help identify metabolic derangements, anemia, electrolyte abnormalities, renal dysfunction, and hepatic dysfunction that can contribute to cognitive impairment 1
- Urinalysis can detect urinary tract infections, which are common precipitants of delirium and cognitive worsening in elderly patients 1
Why Other Options Are Less Appropriate
Patient Health Questionnaire (Depression Screening)
While depression screening is recommended 1, it represents only one component of the comprehensive laboratory evaluation needed. Depression alone does not explain the progressive functional decline described (forgetting to pay utilities, leaving food burning, losing her car), which suggests a neurodegenerative process rather than pure psychiatric illness.
Electroencephalogram (EEG)
EEG is not recommended for routine initial evaluation of dementia 2. It would be appropriate only if:
- Rapidly progressive dementia is suspected (not present in this one-year gradual decline)
- Seizure activity is suspected clinically
- Creutzfeldt-Jakob disease is being considered
Apolipoprotein E Testing
Genetic markers including apolipoprotein E are not recommended for routine diagnostic purposes 1. ApoE testing:
- Does not establish or exclude Alzheimer's disease diagnosis
- Has no role in clinical management decisions
- Is primarily a research tool, not a clinical diagnostic test
Occupational Therapy Referral for IADL Assessment
While eventually valuable for care planning, this is premature before completing the basic medical workup. You must first exclude treatable medical causes of cognitive impairment before proceeding to functional assessments and accommodations 2.
Clinical Pitfalls to Avoid
Do not skip the basic laboratory evaluation even when dementia seems clinically obvious. Reversible causes must be systematically excluded, as thyroid dysfunction, B12 deficiency, and metabolic derangements can present identically to neurodegenerative dementia but are treatable 1.
The clinical presentation described—progressive memory impairment affecting instrumental activities of daily living (IADLs) such as cooking, managing finances, and navigation—is consistent with Alzheimer's disease, but laboratory testing remains mandatory to exclude mimics and comorbidities that could be contributing to or worsening her symptoms 1.