How do I order an Ankle-Brachial Index (ABI) test?

How to Order an Ankle-Brachial Index (ABI) Test

To order an Ankle-Brachial Index (ABI) test, request a "resting ABI with or without segmental pressures and waveforms" through your electronic medical record system or using a vascular laboratory requisition form. 1

Indications for ABI Testing

ABI testing is appropriate for:

1. Patients with symptoms or clinical findings suggestive of PAD 1:

   • Claudication (leg pain with walking that improves with rest)
   • Abnormal lower extremity pulse examination
   • Vascular bruits
   • Non-healing lower extremity wounds
   • Lower extremity gangrene
   • Other suggestive findings (elevation pallor/dependent rubor)

2. Asymptomatic patients at increased risk of PAD 1:

   • Age ≥65 years
   • Age 50-64 years with risk factors for atherosclerosis (diabetes, smoking history, hyperlipidemia, hypertension)
   • Age <50 years with diabetes and one additional atherosclerosis risk factor
   • Known atherosclerotic disease in another vascular bed (coronary, carotid, etc.)

Test Procedure Specifications

When ordering, specify:

• Resting ABI (baseline test)
• Exercise ABI (if symptoms present but resting ABI normal)
• Segmental pressures and waveforms (helps localize disease)
• Toe-Brachial Index (TBI) (for patients with suspected non-compressible vessels)

Preparation Instructions for the Patient

Include these instructions when ordering:

• Rest for 5-10 minutes before the test in a supine position
• Wear loose, comfortable clothing that allows easy access to arms and legs
• Avoid caffeine and tobacco for at least 2 hours before the test
• Maintain a comfortable room temperature

Interpretation Guidelines

ABI results are typically categorized as 1:

• Normal: 1.00-1.40
• Borderline: 0.91-0.99
• Abnormal (PAD): ≤0.90
• Non-compressible vessels: >1.40

Common Pitfalls to Avoid

1. Not measuring both arms: Always measure both arms and use the higher systolic pressure for ABI calculation 1

2. Incorrect patient positioning: Patient should be supine for 5-10 minutes before testing 1

3. Overlooking non-compressible vessels: In patients with diabetes or advanced kidney disease, vessels may be calcified, resulting in falsely elevated ABI (>1.40). In these cases, order a toe-brachial index (TBI) 1

4. Not ordering exercise ABI when appropriate: If resting ABI is normal (>0.90) but symptoms suggest PAD, order an exercise ABI 1

5. Incorrect interpretation of borderline results: ABI values between 0.91-0.99 should be considered borderline and may require additional testing 1

Follow-up Recommendations

When ordering an ABI test, consider including follow-up instructions:

• For abnormal ABI (≤0.90): Schedule vascular consultation
• For borderline ABI (0.91-0.99): Consider exercise ABI or other non-invasive tests
• For non-compressible vessels (>1.40): Order toe-brachial index or other vascular imaging

By following these guidelines, you can ensure appropriate ordering and interpretation of ABI tests for accurate diagnosis and management of peripheral arterial disease.