Laboratory Testing for Epistaxis
For a patient presenting with epistaxis, order a complete blood count (CBC) to assess hemoglobin and platelet count, and if the patient is on warfarin, obtain an INR immediately. 1
Essential Initial Laboratory Tests
For All Patients with Epistaxis
Complete Blood Count (CBC): Order to assess for anemia from blood loss (hemoglobin drop ≥2 g/dL suggests severe bleeding) and to evaluate platelet count for thrombocytopenia. 1
Prothrombin Time (PT): Basic coagulation screening to identify potential bleeding disorders, though this alone is insufficient to diagnose many inherited platelet function disorders. 1, 2
Activated Partial Thromboplastin Time (APTT): Essential coagulation screening, particularly important as prolonged APTT may indicate factor deficiencies or lupus anticoagulant. 1, 3
For Patients on Anticoagulation
International Normalized Ratio (INR): Mandatory for all patients taking warfarin or other vitamin K antagonists, as most patients with epistaxis on warfarin have INR values outside their therapeutic range. 1, 4, 5 Supratherapeutic levels may require specialty consultation or reversal agents for severe refractory bleeding. 6
Renal Function Tests (Creatinine/BUN): Critical for patients on anticoagulants, as renal impairment affects drug clearance and bleeding risk, particularly with low-molecular weight heparins, direct oral anticoagulants, and other renally-cleared agents. 1, 7 Dose adjustments are typically needed when creatinine clearance falls below 30 mL/min. 7
Expanded Testing for Specific Clinical Scenarios
When Bleeding Disorder is Suspected
Order these tests if the patient has: recurrent bilateral epistaxis, family history of bleeding disorders, or bleeding that is difficult to control despite appropriate local measures. 1
von Willebrand Factor (VWF) Panel: Include VWF antigen, ristocetin cofactor activity, and Factor VIII coagulant activity, as von Willebrand disease is the most common inherited bleeding disorder (prevalence ~1%) and epistaxis is its cardinal symptom. 1, 2 Standard PT/APTT/platelet count are insufficient to diagnose VWD. 2
Factor XIII (FXIII) Activity: Consider testing, as FXIII deficiency was found in 6% of hospitalized epistaxis patients in one study and is not detected by routine coagulation screening. 2
Platelet Function Testing: Perform light transmission aggregometry with epinephrine, ADP, collagen, arachidonic acid, and ristocetin if inherited platelet function disorder is suspected, particularly with personal or family bleeding history. 1
Blood Smear: Examine for altered platelet size/structure or other cellular abnormalities (stomatocytosis, neutrophil inclusion bodies) that suggest specific disorders. 1
For Severe or Life-Threatening Bleeding
These criteria define severe bleeding requiring additional workup: posterior epistaxis, hemodynamic instability, hemoglobin drop ≥2 g/dL, or requirement for ≥2 units RBCs. 1
Type and Screen/Crossmatch: Obtain if transfusion is anticipated based on severity of blood loss or hemodynamic instability. 1
Liver Function Tests: Assess in patients with suspected liver disease, as hepatic dysfunction contributes to coagulopathy and bleeding risk. 1
Common Pitfalls to Avoid
Do not rely solely on PT/APTT/platelet count to rule out bleeding disorders, as these miss von Willebrand disease, Factor XIII deficiency, and platelet function disorders. 1, 2
Do not delay local hemostatic measures while waiting for laboratory results; initiate first-line treatments (compression, vasoconstrictors, packing) before considering transfusion or anticoagulation reversal. 1
Do not forget to check INR in warfarin patients, as the majority have out-of-range values contributing to their bleeding. 4, 5
Do not overlook renal function in anticoagulated patients, as impaired renal function dramatically increases bleeding risk and affects anticoagulant dosing. 1, 7
Risk Stratification Based on Laboratory Findings
High-Risk Laboratory Findings Requiring Aggressive Management
- INR >3.0 in warfarin patients with ongoing bleeding 1, 6
- Hemoglobin drop ≥2 g/dL 1
- Platelet count <50,000/μL 1
- Creatinine clearance <30 mL/min in anticoagulated patients 7
- Significantly prolonged APTT not correcting with mixing studies 3
When to Expand Testing Beyond Initial Labs
Recurrent bilateral epistaxis: Screen for hereditary hemorrhagic telangiectasia (HHT) by assessing for nasal/oral telangiectasias and obtaining family history. 1 Consider genetic testing if clinical criteria are met.
Bleeding unresponsive to standard treatment: Pursue comprehensive bleeding disorder workup including VWF panel, Factor XIII, and platelet function studies. 1, 2
Pediatric patients with recurrent epistaxis: Lower threshold for bleeding disorder evaluation, as 13% of hospitalized epistaxis patients have an underlying coagulopathy. 2