Laboratory Evaluation for Poor Memory
For patients presenting with poor memory, obtain a comprehensive metabolic panel (electrolytes, glucose, calcium, BUN, creatinine), complete blood count, thyroid-stimulating hormone (TSH), vitamin B12, and liver function tests as first-line laboratory screening, complemented by brain neuroimaging (preferably MRI). 1
Initial Laboratory Panel (Tier 1)
The following tests should be obtained routinely for all patients with memory complaints:
- Complete Blood Count (CBC) - screens for anemia and infection that can impair cognition 1, 2
- Complete Metabolic Panel including:
- Thyroid-Stimulating Hormone (TSH) - hypothyroidism is a reversible cause of cognitive decline 1, 2
- Vitamin B12 - deficiency causes cognitive impairment 1, 2
- Liver function tests (ALT, AST) - hepatic encephalopathy assessment 1, 3
- Hemoglobin A1c (HbA1c) - evaluate diabetes control 3, 1
This basic panel identified treatable causes of dementia in approximately 5.5% of patients in prospective studies, including hypothyroidism, hyponatremia, hyperparathyroidism, and hypoglycemia 2. These screening tests have definite diagnostic value and should be obtained before pursuing more expensive or invasive testing. 2
Neuroimaging (Tier 1)
- Brain MRI (non-contrast) is the preferred initial imaging modality to evaluate for structural causes including stroke, white matter disease, atrophy patterns, hydrocephalus, and space-occupying lesions 1, 3
- CT scan is acceptable if MRI is contraindicated or unavailable, with coronal reformations recommended to assess hippocampal atrophy 3, 1
Additional Testing Based on Clinical Context (Tier 2)
Consider these tests when clinical features suggest specific etiologies:
- Lipid panel - for vascular risk stratification 1, 3
- Syphilis serology (RPR, FTA-ABS) - in atypical presentations or risk factors 1
- HIV serology - in appropriate clinical contexts 1
- ESR and CRP - when inflammatory or autoimmune causes suspected 1
- Antithyroid antibodies (anti-TPO, anti-thyroglobulin) - to rule out Hashimoto's encephalopathy 1
- Homocysteine - may be considered though evidence is limited 1
Specialized Testing (Tier 3-4)
Reserve these for complex, atypical, or rapidly progressive cases:
- Lumbar puncture with CSF analysis - for early-onset dementia (<65 years), rapidly progressive dementia, or when autoimmune/infectious/paraneoplastic causes are suspected 1, 3
- Advanced neuroimaging (FDG-PET, amyloid PET, SPECT) - for diagnostically uncertain cases 1
- Blood biomarkers for amyloid pathology - emerging tools that may reduce need for CSF or PET imaging in appropriate clinical contexts (patients with objective cognitive impairment where AD is suspected after comprehensive workup) 3, 4
Critical Clinical Considerations
A careful history and physical examination must accompany laboratory testing - most dementia diagnoses, including Alzheimer's disease (74.5% of cases), are made primarily from clinical assessment rather than laboratory findings 2. The laboratory evaluation serves to identify the minority of treatable causes and exclude metabolic contributors.
Common pitfall: Ordering extensive testing without clinical indication increases costs without improving diagnostic yield. A selective approach based on history, examination, and screening tests reduces charges by 25-34% compared to routine comprehensive testing 2.
For hepatic encephalopathy specifically: If liver disease is present, blood ammonia levels may be helpful but hyperammonemia can occur without encephalopathy 3. Clinical assessment remains paramount.
Cognitive testing should accompany laboratory evaluation - validated instruments like the MoCA (more sensitive for mild cognitive impairment) or MMSE help establish objective cognitive impairment 3. However, cognitive screening in patients with memory complaints does not reliably identify those requiring dementia workup, as most dementia patients lack documented memory complaints 5.