What blood work is indicated for a suspected stroke?

Blood Work for Suspected Stroke

For all patients with suspected stroke, essential blood work includes blood glucose, complete blood count with platelet count, coagulation studies (PT/INR, aPTT), serum electrolytes, renal function tests, cardiac markers, and oxygen saturation measurement. 1

Core Laboratory Tests for All Suspected Stroke Patients

Immediate Priority Tests

• Blood glucose: Critical to identify hypoglycemia which can mimic stroke symptoms 1
• Complete blood count (CBC) with platelet count: Identifies bleeding disorders or thrombocytopenia 1
• Coagulation studies:
  • Prothrombin time (PT)/International Normalized Ratio (INR)
  • Activated partial thromboplastin time (aPTT)
  • Essential before thrombolytic therapy 1
• Serum electrolytes and renal function tests: Identify metabolic causes of neurological symptoms 1
• Cardiac markers: Detect concurrent myocardial ischemia which can cause or result from stroke 1
• Oxygen saturation: Identifies hypoxia which can worsen brain injury 1

Important Timing Consideration

While these tests should be performed for all suspected stroke patients, they should not delay neuroimaging or treatment decisions for thrombolytic therapy unless:

1. There is clinical suspicion of bleeding abnormality or thrombocytopenia
2. The patient has received anticoagulants (heparin, warfarin, direct thrombin inhibitors, or factor Xa inhibitors)
3. Anticoagulant use is uncertain 1

Additional Tests for Selected Patients

Based on clinical presentation and history, additional tests may be indicated:

• Hepatic function tests: For patients with liver disease or suspected toxin ingestion 1
• Toxicology screen: When drug intoxication is suspected 1
• Blood alcohol level: When alcohol intoxication is suspected 1
• Pregnancy test: For women of childbearing age 1
• Arterial blood gas: When hypoxia is suspected 1
• Thrombin time (TT) or ecarin clotting time (ECT): For patients suspected to be taking direct thrombin inhibitors or direct factor Xa inhibitors 1

Laboratory Testing for Secondary Prevention

For ongoing management and secondary prevention, additional tests should be considered:

• HbA1c: To assess long-term glucose control 1, 2
• Lipid profile: For assessment of dyslipidemia as a risk factor 1, 2

Clinical Pearls and Pitfalls

• Do not delay thrombolysis: Time is critical in acute stroke management. Laboratory results should not delay thrombolytic therapy unless specific concerns exist about coagulation abnormalities 1
• Hypoglycemia mimics stroke: Always check blood glucose immediately as hypoglycemia can present with focal neurological deficits similar to stroke 1
• Cardiac-stroke connection: Cardiac abnormalities are prevalent among stroke patients. ECG and cardiac markers are essential as acute myocardial infarction can lead to stroke and vice versa 1
• Coagulation prediction: In emergency situations, elevated PT/PTT can be predicted with high sensitivity and specificity in patients taking warfarin or heparin/heparinoid or on hemodialysis, potentially reducing treatment delays 3

By following these evidence-based laboratory testing recommendations, clinicians can efficiently diagnose stroke, rule out stroke mimics, and guide appropriate acute management and secondary prevention strategies.