Initial Diagnostic Test for Peripheral Vascular Disease
The resting ankle-brachial index (ABI), with or without pulse volume recordings and/or Doppler waveforms, is the cornerstone initial diagnostic test to establish the diagnosis of peripheral vascular disease. 1
How to Perform and Interpret the Resting ABI
Measure systolic blood pressures in both arms (brachial arteries) and both ankles (dorsalis pedis and posterior tibial arteries) using a Doppler device with the patient supine 1
Calculate the ABI for each leg by dividing the higher of the dorsalis pedis or posterior tibial pressure by the higher of the right or left arm blood pressure 1
Report results as: 1
- Abnormal: ABI ≤0.90 (confirms PAD diagnosis)
- Borderline: ABI 0.91-0.99
- Normal: ABI 1.00-1.40
- Noncompressible: ABI >1.40 (calcified vessels)
When the Resting ABI is Insufficient
If the resting ABI is >1.40 (noncompressible vessels), proceed immediately to toe-brachial index (TBI) with waveforms to establish the diagnosis, as this occurs commonly in patients with diabetes and chronic kidney disease 1
If the patient has exertional leg symptoms but the resting ABI is normal or borderline (>0.90 and ≤1.40), perform exercise treadmill ABI testing to unmask PAD, as nearly half of symptomatic patients may have normal resting ABI values 1, 2
- A post-exercise ABI decrease of >20% or an ABI falling below 0.90 after exercise confirms PAD 1, 2
- Research demonstrates that 31% of symptomatic patients with normal resting ABI will have abnormal post-exercise ABI 2
Additional Physiological Testing
Segmental leg pressures with pulse volume recordings (PVR) and/or Doppler waveforms can be performed alongside the resting ABI to help localize the anatomic level of disease (aortoiliac, femoropopliteal, infrapopliteal) 1
For suspected chronic limb-threatening ischemia (CLTI), add toe pressure/TBI, transcutaneous oxygen pressure (TcPO2), and/or skin perfusion pressure (SPP) in addition to ABI to assess arterial perfusion and establish CLTI diagnosis 1
Common Pitfalls to Avoid
Do not screen asymptomatic patients without risk factors for PAD with ABI, as this is not recommended 1
Do not stop at a normal resting ABI in symptomatic patients – nearly half of patients referred for suspected PAD have normal resting ABI but require exercise testing or additional evaluation 2
Do not rely on ABI alone in diabetic patients or those with suspected noncompressible vessels (ABI >1.40), as calcification renders the test unreliable; proceed directly to TBI 1
Avoid anatomic imaging (duplex ultrasound, CTA, MRA, angiography) as initial diagnostic tests – these are reserved for patients in whom revascularization is being considered after PAD is confirmed physiologically 1