From the Guidelines
The initial diagnostic test for Peripheral Arterial Disease (PAD) should be the resting Ankle-Brachial Index (ABI) test, as it is a simple, non-invasive, and effective method for establishing the diagnosis and guiding further management. The ABI test compares blood pressure in the ankle to blood pressure in the arm, with a ratio below 0.9 indicating PAD 1. To perform the test, blood pressure measurements are taken at both arms and both ankles using a blood pressure cuff and Doppler ultrasound device.
Diagnostic Tests for PAD
The following diagnostic tests may be used to diagnose PAD:
- Resting Ankle-Brachial Index (ABI) test: This is the initial diagnostic test for PAD and may be the only test required to establish the diagnosis and institute guideline-directed medical therapy (GDMT) 1.
- Segmental pressure measurements: These measurements can be used to localize anatomic segments of disease (e.g., aortoiliac, femoropopliteal, infrapopliteal) 1.
- Pulse volume recordings: These recordings can be used to assess perfusion in patients with suspected PAD 1.
- Exercise treadmill ABI testing: This test is important to objectively measure functional limitations attributable to leg symptoms and is useful in establishing the diagnosis of lower extremity PAD in the symptomatic patient when resting ABIs are normal or borderline 1.
- Measurement of the toe-brachial index (TBI): The TBI is used to establish the diagnosis of PAD in the setting of non-compressible arteries (ABI >1.40) and may also be used to assess perfusion in patients with suspected critical limb ischemia (CLI) 1.
- Anatomic imaging assessment: Studies such as duplex ultrasound, computed tomography angiography (CTA), magnetic resonance angiography (MRA), or invasive angiography are generally reserved for highly symptomatic patients in whom revascularization is being considered 1.
Indications for Diagnostic Testing
Diagnostic testing for PAD should be considered in patients with:
- Symptoms of claudication or CLI
- Risk factors for PAD, such as smoking, diabetes, hypertension, high cholesterol, or age over 65
- Inconclusive ABI and physiological testing results 1
- Asymptomatic patients with multiple risk factors, as many patients with PAD do not experience typical symptoms.
According to the 2024 ACC/AHA/AACVPR/APMA/ABC/SCAI/SVM/SVN/SVS/SIR/VESS guideline, in patients with functionally limiting claudication with inadequate response to GDMT for whom revascularization is being considered, duplex ultrasound, CTA, MRA, or catheter angiography of the lower extremities is useful for assessment of anatomy and severity of disease and to determine potential revascularization strategy 1.
From the Research
Diagnostic Tests for Peripheral Arterial Disease (PAD)
The following diagnostic tests are used to confirm the diagnosis of PAD and determine its severity and extent:
- Ankle-brachial index (ABI) 2, 3, 4, 5, 6
- Segmental limb pressures 2
- Pulse volume recordings 2
- Duplex ultrasonography 2, 3
- Computed tomography angiography 2
- Magnetic resonance angiography 2
- Toe-brachial index (TBI) 5, 6
Non-Invasive Tests
Non-invasive vascular testing is recommended for most patients suspected of having PAD 2. These tests include:
- ABI, which is a simple and inexpensive diagnostic test for PAD 4
- TBI, which is useful for detecting stenosis in PAD, especially in patients with normal or low ABI values 5, 6
- Duplex ultrasonography, which is a reliable and non-invasive examination for detecting PAD 3
Limitations of Diagnostic Tests
The ABI has variable accuracy for identification of significant stenosis 4 and may be unreliable in patients with vascular stiffness or diabetes 5. The TBI has a higher sensitivity and specificity for detecting vessel stenosis, but its diagnostic criteria are not strictly evidence-based 5. Further studies are needed to establish the risk of morbidity and mortality for the various diagnostic limits of the TBI 5.