What blood work should be ordered for a confused patient?

Blood Work for Confused Patients

For a confused patient, a comprehensive panel of blood tests should be ordered including complete blood count, basic metabolic panel, liver function tests, thyroid function tests, and toxicology screening to identify potential underlying causes of confusion. 1

Core Laboratory Tests

Essential First-Line Tests

• Complete blood count (CBC) to assess for anemia, infection, or hematologic abnormalities that may contribute to confusion 1, 2
• Serum electrolytes (sodium, potassium, chloride) to identify electrolyte imbalances that can cause altered mental status 1
• Blood glucose to rule out hypoglycemia or hyperglycemia as causes of confusion 1
• Renal function tests (BUN, creatinine) to evaluate for uremia or other metabolic derangements 1, 3
• Liver function tests to assess for hepatic encephalopathy or other liver-related causes of confusion 1
• Calcium and other minerals to identify hypercalcemia or other mineral imbalances 1, 4
• Prothrombin time/international normalized ratio (INR) to evaluate coagulation status, especially if stroke is suspected 1

Second-Line Tests

• Thyroid function tests (TSH) to rule out thyroid disorders that can present with confusion 1, 4
• Cardiac enzymes (troponin) to evaluate for cardiac ischemia which may present with confusion in elderly patients 1
• Arterial blood gas analysis if hypoxia is suspected as a cause of confusion 1
• Toxicology screening when drug intoxication or withdrawal is suspected 1
• Ammonia levels if hepatic encephalopathy is suspected 1

Specialized Testing Based on Clinical Context

For Suspected Stroke

• If stroke is suspected as a cause of confusion, additional tests should include:
  • Complete coagulation profile (PT/INR, aPTT) 1
  • Cardiac markers to rule out cardiac causes of stroke 1
  • Consider ECG monitoring for at least 24 hours to detect paroxysmal atrial fibrillation 1

For Suspected Infection

• If infection is suspected:
  • Blood cultures if fever or other signs of infection are present 1
  • Inflammatory markers (C-reactive protein, procalcitonin) 1
  • Consider lumbar puncture if meningitis or encephalitis is suspected 1

For Suspected Metabolic Disorders

• If metabolic disorders are suspected:
  • HbA1c to evaluate for undiagnosed diabetes 1, 4
  • Lipid profile to assess for dyslipidemia which may contribute to vascular causes of confusion 1, 4

Clinical Considerations and Pitfalls

• The extent of laboratory abnormalities does not necessarily correlate with clinical significance - even mild abnormalities can indicate serious underlying conditions 1
• Simply repeating abnormal tests without investigating the underlying cause is not recommended unless there is high certainty that the abnormality will resolve 1
• Laboratory results should always be interpreted in the context of the patient's clinical presentation 1, 5
• When ordering tests for confused patients, consider the pre-test probability of various conditions based on age, comorbidities, and presentation 5
• In elderly patients, multiple causes of confusion often coexist, requiring a broader testing approach 1

Time-Sensitive Considerations

• For acute confusion with suspected stroke, laboratory tests should not delay neuroimaging or potential thrombolytic therapy 1
• If critical values are identified (severe electrolyte abnormalities, profound hypoglycemia), immediate treatment should be initiated while awaiting complete results 1
• In cases of suspected drug overdose or toxicity, specific antidotes may need to be administered before complete test results are available 1