What laboratory tests are recommended for a patient with suspected stroke and potential underlying conditions such as atrial fibrillation, hypertension, or diabetes?

Laboratory Tests for Suspected Stroke

All patients with suspected stroke should immediately receive a core panel of laboratory tests including complete blood count with platelets, electrolytes, renal function (creatinine, eGFR), coagulation studies (aPTT, INR), random glucose or HbA1c, and troponin, along with a 12-lead ECG. 1

Initial Laboratory Workup

The following tests should be obtained routinely as part of the initial evaluation:

Core Laboratory Panel

• Complete blood count (CBC) - Essential to detect thrombocytopenia, anemia, or polycythemia that could influence treatment decisions 1
• Electrolytes - Necessary to identify metabolic derangements that can affect management 1
• Renal function (creatinine, eGFR) - Critical for medication dosing and identifying renal dysfunction 1
• Coagulation studies (aPTT, INR) - Particularly important to identify coagulopathies and assess anticoagulant use, especially before considering thrombolytic therapy 1
• Random glucose or HbA1c - Hypoglycemia can mimic stroke symptoms and must be ruled out immediately; hyperglycemia is associated with worse outcomes 1
• Troponin - Identifies concurrent cardiac conditions, as acute MI can cause stroke and stroke can precipitate myocardial ischemia 1

Cardiac Evaluation

• 12-lead ECG - Mandatory to assess cardiac rhythm and identify atrial fibrillation, atrial flutter, or evidence of structural heart disease (myocardial infarction, left ventricular hypertrophy) 1
• ECG monitoring >24 hours - Recommended as part of initial stroke workup to detect paroxysmal atrial fibrillation in patients who would be potential candidates for anticoagulant therapy 1

Subsequent Laboratory Tests

These may be considered during the patient encounter or as an outpatient:

• Lipid profile (fasting or non-fasting) - For cardiovascular risk assessment 1
• Diabetes screening - Using fasting plasma glucose, 2-hour plasma glucose, HbA1c, or 75g oral glucose tolerance test if not already obtained 1

Additional Testing for Specific Scenarios

For Embolic Stroke of Undetermined Source (ESUS)

• Prolonged ECG monitoring for at least 2 weeks - Recommended to improve detection of paroxysmal atrial fibrillation in selected patients aged ≥55 years who are not already receiving anticoagulant therapy but would be potential candidates 1
• Echocardiography - Should be considered when stroke mechanism has not been identified 1

For Hemorrhagic Stroke

When hemorrhagic stroke is confirmed or suspected, additional tests include:

• Hepatic function tests - Particularly important in patients with suspected liver disease or alcohol use 2
• Toxicology screen - When drug use is suspected or clinical presentation is atypical 2
• Blood alcohol level - When alcohol intoxication is suspected 2
• Pregnancy test - For women of childbearing age 2
• Arterial blood gas - When hypoxia is suspected or in patients with respiratory compromise 2

Critical Timing Considerations

Acute treatment (such as thrombolytic therapy) should not be delayed while awaiting laboratory results unless there is clinical suspicion of bleeding abnormality, thrombocytopenia, or known anticoagulant use. 3

• The diagnostic evaluation should be completed or underway within 48 hours of symptom onset 3
• Blood glucose testing should be performed immediately as hypoglycemia can mimic stroke and must be excluded before proceeding with other interventions 1

Common Pitfalls to Avoid

• Do not delay imaging or treatment while waiting for all laboratory results unless coagulopathy or bleeding disorder is suspected 3
• Do not assume normal glucose - always verify with point-of-care testing as hypoglycemia is a critical stroke mimic 1
• Do not rely on short-term cardiac monitoring alone - if cardioembolic mechanism is suspected but initial ECG is negative, prolonged monitoring is essential 1
• Do not order routine thrombophilia testing for most patients with arterial thrombosis, except in specific scenarios such as young patients lacking traditional atherosclerotic risk factors 3