What is the typical workup for peripheral artery disease (PAD)?

Diagnostic Workup for Peripheral Artery Disease (PAD)

The initial diagnostic test for suspected peripheral artery disease should be the resting ankle-brachial index (ABI), with or without segmental pressures and waveforms, to establish the diagnosis. 1

Patient Identification and Risk Assessment

High-Risk Patients Who Should Be Screened

• Age ≥65 years 1
• Age 50-64 years with risk factors for atherosclerosis (diabetes mellitus, smoking history, hyperlipidemia, hypertension) or family history of PAD 1
• Age <50 years with diabetes mellitus and one additional risk factor for atherosclerosis 1
• Individuals with known atherosclerotic disease in another vascular bed (coronary, carotid, subclavian, renal, mesenteric artery stenosis, or abdominal aortic aneurysm) 1

Clinical Assessment

• Comprehensive medical history and review of symptoms to assess for exertional leg symptoms, including claudication, walking impairment, ischemic rest pain, and nonhealing wounds 1
• Vascular examination including palpation of lower extremity pulses (femoral, popliteal, dorsalis pedis, posterior tibial), auscultation for femoral bruits, and inspection of legs and feet 1
• Noninvasive blood pressure measurement in both arms (to identify potential subclavian artery stenosis and determine the highest systolic pressure for accurate ABI calculation) 1

Diagnostic Testing Algorithm

Step 1: Initial Testing

• Resting ABI - The primary diagnostic test for PAD 1
  • ABI ≤0.90: Abnormal (confirms PAD diagnosis) 1, 2
  • ABI 0.91-0.99: Borderline 1
  • ABI 1.00-1.40: Normal 1
  • ABI >1.40: Noncompressible arteries 1

Step 2: Additional Testing Based on Initial Results

For Normal or Borderline ABI (0.91-1.40) with Symptoms Suggestive of PAD:

• Exercise treadmill ABI testing - Important to objectively measure functional limitations and establish PAD diagnosis when resting ABIs are normal or borderline 1
  • A post-exercise ABI decrease of >20% is diagnostic for PAD 1

For Noncompressible Arteries (ABI >1.40):

• Toe-brachial index (TBI) - Should be measured to diagnose PAD when ABI >1.40 1
  • TBI <0.70 is diagnostic for PAD 1
• Alternative tests - Doppler waveform analysis or pulse volume recordings 1

For Patients with Diabetes or Renal Failure:

• Toe pressure (TP) or TBI is recommended even if resting ABI is normal 1
• Transcutaneous oxygen pressure (TcPO2) may be considered for assessing tissue perfusion 1

Step 3: Anatomic Assessment for Revascularization Candidates

• Duplex ultrasound - Recommended as first-line imaging method to confirm PAD lesions 1
• Computed tomography angiography (CTA) - For anatomical characterization of PAD lesions 1
• Magnetic resonance angiography (MRA) - For anatomical characterization of PAD lesions 1
• Invasive angiography - Generally reserved for patients undergoing revascularization procedures 1

Special Considerations

For Patients with Chronic Wounds:

• Apply the Wound, Ischemia, and foot Infection (WIfI) classification system to estimate individual risk of amputation 1
• Assess for critical limb perfusion parameters:
  • Ankle pressure <50 mmHg 1
  • Toe pressure <30 mmHg 1
  • TcPO2 <30 mmHg 1

For Patients with Atypical Symptoms:

• Consider alternative causes of leg pain if ABI and physiological testing are normal 1
• Assess for "masked PAD" in patients with reduced walking capacity due to other conditions or reduced pain sensitivity 1

Common Pitfalls to Avoid

• Failing to measure blood pressure in both arms, which can lead to inaccurate ABI calculations 1
• Not considering exercise ABI testing when resting ABI is normal but clinical suspicion for PAD is high 1, 2
• Relying solely on classic claudication symptoms, as only about 10% of patients with PAD present with these classic symptoms 2, 3
• Not using TBI or alternative tests in patients with diabetes or renal disease who may have noncompressible arteries 1, 4
• Performing invasive angiography in asymptomatic PAD patients, which is not recommended 1