What is the initial test for suspected new onset Peripheral Artery Disease (PAD)?

Initial Testing for Suspected New Onset Peripheral Artery Disease (PAD)

The resting ankle-brachial index (ABI) is the recommended initial diagnostic test for patients with suspected new onset peripheral artery disease (PAD). 1

Patient Selection for ABI Testing

ABI testing should be performed in patients who:

1. Have history or physical examination findings suggestive of PAD:

   • Exertional leg symptoms (claudication or other walking impairment)
   • Ischemic rest pain
   • Nonhealing wounds
   • Abnormal lower extremity pulse examination

2. Are at increased risk of PAD but without symptoms:

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

ABI Testing Procedure

The resting ABI is performed by:

• Measuring systolic blood pressures at the arms (brachial arteries)
• Measuring systolic blood pressures at the ankles (dorsalis pedis and posterior tibial arteries)
• Using a Doppler device with patient in supine position
• Calculating ABI by dividing the higher ankle pressure by the higher arm pressure for each leg

Interpretation of ABI Results

ABI results should be reported as:

• Abnormal: ≤0.90 (indicates PAD)
• Borderline: 0.91-0.99 (requires further evaluation)
• Normal: 1.00-1.40
• Noncompressible: >1.40 (indicates arterial calcification)

Additional Testing When Indicated

1. For patients with noncompressible vessels (ABI >1.40):

   • Toe-brachial index (TBI) should be measured 1

2. For patients with normal or borderline ABI but exertional symptoms:

   • Exercise treadmill ABI testing should be performed 1
   • This can unmask PAD in up to 31% of symptomatic patients with normal resting ABI 2

3. For patients with confirmed PAD being considered for revascularization:

   • Duplex ultrasound, CT angiography, or MR angiography to assess anatomic location and severity 1

Common Pitfalls and Caveats

1. Relying solely on symptoms:

   • Only about 10% of PAD patients experience classic claudication 3
   • 50% have atypical leg symptoms
   • 40% have no leg symptoms at all

2. Failure to perform exercise ABI when indicated:

   • Normal resting ABI doesn't exclude PAD in symptomatic patients
   • Exercise testing significantly increases diagnostic sensitivity 2

3. Inappropriate ABI screening:

   • ABI is not recommended for patients not at increased risk and without suggestive symptoms 1

4. Inadequate technique:

   • Automated oscillometric methods may be more accurate than manual Doppler when performed by inexperienced operators 4
   • Proper training in ABI measurement is essential

5. Underutilization:

   • Despite being a grade 1, level A recommendation, ABI is underutilized in clinical practice 5
   • Failure to perform ABI may lead to missed diagnoses and inappropriate interventions

By following these guidelines for ABI testing, clinicians can accurately diagnose PAD, assess disease severity, and guide appropriate management decisions to improve patient outcomes.