Laboratory Tests for Adult Acute Ischemic Stroke Evaluation
All adult patients with suspected acute ischemic stroke being evaluated for thrombolysis should immediately receive: complete blood count with platelets, basic metabolic panel (electrolytes, renal function), serum glucose, PT/INR, aPTT, cardiac troponin, and 12-lead ECG. 1, 2
Core Laboratory Panel (All Patients)
Immediate Priority Tests
- Blood glucose must be checked immediately as hypoglycemia can mimic stroke symptoms and requires urgent exclusion before any other intervention 1, 2, 3
- Complete blood count with platelet count is essential to detect thrombocytopenia (which contraindicates thrombolysis), anemia, or polycythemia that could influence treatment decisions 1, 2, 4
- Serum electrolytes and renal function tests (including creatinine) identify metabolic derangements that can mimic stroke and guide medication dosing 1, 2, 4
- PT/INR and aPTT are critical to identify coagulopathies, especially in patients on warfarin or with suspected bleeding abnormalities 1, 2, 4
- Cardiac troponin identifies concurrent myocardial infarction or ischemia, as acute MI can cause stroke and stroke can precipitate myocardial ischemia 1, 2, 4
- 12-lead ECG is mandatory to detect atrial fibrillation, atrial flutter, or acute myocardial infarction 1, 2, 4
- Oxygen saturation should be monitored continuously 1, 2, 3
Critical Timing Consideration for Thrombolysis
Thrombolytic therapy should NOT be delayed while awaiting coagulation results (PT/INR, aPTT, platelet count) UNLESS: 1, 2
- There is clinical suspicion of bleeding abnormality or thrombocytopenia
- The patient has received heparin or warfarin
- Anticoagulant use is uncertain
Additional Tests for Specific Clinical Scenarios
For Patients on Anticoagulation
- Anticoagulant-specific levels should be obtained if the patient is on direct oral anticoagulants (DOACs) 5
- Calibrated anti-Xa activity for apixaban, edoxaban, rivaroxaban
- Hemoclot assay for dabigatran
- Levels <50 ng/mL support thrombolysis consideration; levels >100 ng/mL exclude thrombolysis 5
- INR ≥2.0 makes ischemia far less likely in warfarin patients; no patient with INR ≥3.6 had ischemia in validation studies 6
For Selected Patients Based on Clinical Suspicion
- Hepatic function tests if liver dysfunction is suspected or patient is on warfarin 1, 2, 7
- Toxicology screen and blood alcohol level if drug or alcohol use is suspected 1, 2, 4
- Pregnancy test (serum β-hCG) for females of childbearing potential 1, 2, 4
- Arterial blood gas only if hypoxia is suspected 1, 2, 4
- Chest radiography only if lung disease is clinically suspected (routine chest X-ray altered management in only 3.8% of stroke patients) 2, 4
- Lumbar puncture only if subarachnoid hemorrhage is suspected and CT scan is negative for blood 1, 2, 4
- ESR and CRP only if vasculitis is specifically suspected (not routine) 8
Secondary Risk Stratification Tests (Within 48 Hours)
- Lipid profile for cardiovascular risk assessment 9, 10
- HbA1c for diabetes screening if not already obtained 9, 10
- Extended cardiac monitoring for at least 14 days if initial ECG shows no atrial fibrillation but embolic mechanism is suspected 9, 11, 10
Common Pitfalls to Avoid
- Never delay thrombolysis for routine coagulation studies unless specific contraindications exist (known anticoagulant use, clinical bleeding suspicion, or thrombocytopenia) 1, 2
- Do not skip glucose testing - it is the only stroke mimic requiring immediate exclusion 3, 10
- Do not order routine chest X-ray unless clinically indicated by respiratory symptoms 2, 4
- Do not delay treatment for HbA1c, lipid profile, or other secondary tests - these can be obtained after acute management 9
- Label specimens STAT if patient is within thrombolysis window to expedite processing 7