What is the PenFAST score and how is it applied to determine the need for emergent head computed tomography in patients with minor head injury who are on anticoagulant or antiplatelet therapy?

PenFAST Score for Head CT Decision-Making in Anticoagulated Patients

Critical Clarification: PenFAST Score Is Not Validated or Recommended

The PenFAST score is not mentioned in current American College of Emergency Physicians (ACEP) guidelines, and no validated clinical decision tool currently exists for determining the need for head CT in patients on anticoagulants or antiplatelet therapy after minor head injury. 1

Current Evidence-Based Approach

Immediate Imaging Indications

All patients on anticoagulants or antiplatelet agents (excluding aspirin monotherapy) who sustain any head trauma require immediate non-contrast head CT, regardless of mechanism severity, presence of symptoms, or Glasgow Coma Scale score. 2, 3

• The Canadian CT Head Rule (CCHR) and New Orleans Criteria (NOC) are only valid for patients NOT on anticoagulants and cannot be applied to anticoagulated patients 1
• Anticoagulated patients have a 2.6-fold increased risk of significant intracranial injury (3.9% vs 1.5% in non-anticoagulated patients) 3
• Even patients with GCS 15 and no loss of consciousness have a 29% rate of intracranial hemorrhage when anticoagulated 2, 4

Risk Stratification by Medication Type

The risk varies significantly by anticoagulant/antiplatelet agent:

• Warfarin: 10.2% incidence of intracranial hemorrhage (highest risk) 2, 3
• Direct oral anticoagulants (DOACs): 2.6% incidence 2, 3
• Combined aspirin + clopidogrel: Relative risk 2.88 (highest among combinations) 3
• Clopidogrel alone: Dramatically elevated mortality (OR 14.7) 2
• Aspirin monotherapy: Relative risk 1.29 (95% CI 0.88-1.87), not considered mandatory imaging criterion by itself 3

Critical Clinical Predictors

When evaluating anticoagulated patients with head trauma, document these high-risk features:

• Loss of consciousness: Strongest predictor of intracranial hemorrhage (Wald=7.468, p=0.008) 4
• Post-traumatic amnesia or confusion: Significantly increases risk 2
• INR >3.0: Relative risk of delayed hemorrhage = 14 (95% CI 4-49) 5
• Age >65 years: Ground-level falls account for 34.6% of trauma deaths in this population 2
• GCS <15: Requires imaging even without other criteria 2

Management Algorithm After Initial CT

If Initial CT Shows Hemorrhage:

1. Immediately discontinue all anticoagulants/antiplatelets 2, 3
2. Obtain urgent neurosurgical consultation 3
3. Reverse anticoagulation urgently using agent-specific protocols:
   • Warfarin: 4-factor PCC + 5mg IV vitamin K, target INR <1.5 2, 3
   • Apixaban/rivaroxaban: Andexanet alfa (or 2000 units 4F-PCC if unavailable) 2, 3
   • Dabigatran: Idarucizumab 5g IV (or 50 units/kg activated PCC if unavailable) 2, 3
4. Obtain repeat head CT within 24 hours: Anticoagulated patients have 3-fold increased risk of hemorrhage expansion (26% vs 9%) 3, 5

If Initial CT Is Negative:

Neurologically intact patients (GCS 15, baseline mental status, no focal deficits) with negative initial CT can be safely discharged without repeat imaging or prolonged observation. 1, 2

• Risk of delayed intracranial hemorrhage requiring intervention is extremely low (<1%) 2, 3
• Do not routinely discontinue anticoagulation after negative CT, as thromboembolic risk may outweigh the small risk of delayed hemorrhage 1, 3
• ACEP Level B recommendation: Do not routinely perform repeat imaging or admit/observe these patients 1

Consider Brief Observation (4-6 hours) If:

• Age >80 years with loss of consciousness or amnesia 2, 3
• Initial INR >3.0 5
• Multiple anticoagulant/antiplatelet agents 2

Discharge Instructions (Mandatory)

Provide written instructions including:

• Warning signs of delayed hemorrhage: Severe headache, vomiting, confusion, weakness, seizure—instruct to call 911 immediately 1, 2
• Outpatient referral for fall risk assessment 1, 2
• Reassessment of anticoagulation risk/benefit ratio 1, 2

Common Pitfalls to Avoid

• Do not withhold CT based on "minor mechanism": Mechanism severity does not predict intracranial injury in anticoagulated elderly patients 2
• Do not apply CCHR or NOC to anticoagulated patients: These tools explicitly exclude patients on anticoagulation 1
• Do not perform routine repeat CT in stable patients with negative initial scan: This adds unnecessary cost and radiation without improving outcomes 1, 3
• Do not automatically discontinue anticoagulation after negative CT: Balance thromboembolic risk against the <1% risk of delayed hemorrhage 2, 3