Laboratory Workup for Elderly Female with Confusion and Disorientation
Order a targeted laboratory panel including complete blood count (CBC), comprehensive metabolic panel (CMP), thyroid function tests (TSH), vitamin B12 level, urinalysis, and urine toxicology screen based on the clinical presentation of acute confusion in this elderly patient. 1, 2
Essential Initial Laboratory Tests
The following tests should be ordered immediately for any elderly patient presenting with new confusion and disorientation:
- Complete Blood Count (CBC) - identifies infection, anemia, and hematologic abnormalities that commonly cause delirium in elderly patients 1, 3
- Comprehensive Metabolic Panel (CMP) - detects electrolyte disturbances (particularly hyponatremia and hypercalcemia), renal failure, hepatic dysfunction, and glucose abnormalities; electrolyte abnormalities were found in 6% of elderly patients with mental status changes 1, 3
- Thyroid Function Tests (TSH, free T4) - screens for both hyperthyroidism and hypothyroidism, which are potentially reversible causes of confusion; thyroid dysfunction was newly diagnosed in 3% and exacerbated in 6% of elderly patients with mental status changes 1, 2, 3
- Vitamin B12 Level - identifies B12 deficiency, a reversible cause of cognitive impairment and confusion in elderly patients 1, 2
- Urinalysis with Culture - detects urinary tract infection, which is a leading cause of delirium in elderly patients; bacteriuria was found in 13% of elderly patients presenting with mental status changes 1, 3
- Urine Toxicology Screen - rules out substance intoxication or withdrawal, particularly important given that 30% of psychiatric presentations may have toxicologic etiologies 4, 1
Clinical Context for Laboratory Selection
History and physical examination should guide additional testing beyond the core panel. The evidence demonstrates that history has 94% sensitivity for identifying medical conditions causing psychiatric symptoms, while laboratory studies alone have only 20% sensitivity. 4
Additional Tests Based on Clinical Findings:
- Medication levels (digoxin, anticonvulsants, lithium) if patient takes these medications - medication reactions were found in 7% of elderly patients with mental status changes 3
- Arterial blood gas if hypoxia or hypercarbia suspected based on vital signs or respiratory examination 2
- Blood cultures if fever present or sepsis suspected 2
- Ammonia level if hepatic encephalopathy suspected based on liver disease history 2
- Rapid plasma reagin (RPR) if risk factors for neurosyphilis present 2
- HIV testing if risk factors present, as HIV infection is an irreversible cause of dementia 2
Important Clinical Distinctions
Delirium must be assumed until proven otherwise in any elderly patient with acute confusion. 2 The key distinction is:
- Delirium - acute onset, fluctuating course, often reversible with treatment of underlying medical cause 2
- Dementia - gradual onset, progressive course, may have some reversible causes (thyroid dysfunction, B12 deficiency, normal-pressure hydrocephalus) 2
The Confusion Assessment Method should be used to evaluate for delirium if there is concern about acute confusional state. 4
Common Pitfalls to Avoid
Do not assume a primary psychiatric disorder without adequate medical workup in elderly patients. Approximately 20% of acute psychosis cases have medical etiologies, with elderly patients at particularly high risk for organic causes. 1 History and physical examination identify the vast majority of medical problems, but targeted laboratory testing is essential to detect conditions like electrolyte abnormalities that may not be clinically apparent. 4
Avoid ordering extensive screening tests without clinical indication. Head CT scanning, electroencephalography, and chest radiography did not affect management when used as routine screening tests in elderly patients with mental status changes. 3 These should be reserved for patients with focal neurologic findings, head trauma, or specific clinical indications. 2
Do not overlook medication-related causes. Review all medications including over-the-counter drugs and recent medication changes, as medication reactions are common in elderly patients with confusion. 3