Diagnoses Supporting ABI Ultrasound Order
Order an ABI ultrasound for patients with suspected peripheral artery disease (PAD), specifically those with exertional leg symptoms, nonhealing wounds, age ≥65 years, or age ≥50 years with smoking history or diabetes. 1
Primary Diagnostic Indications (Class I Recommendations)
The most recent 2016 AHA/ACC guidelines provide clear criteria for when ABI testing is indicated 1:
Symptomatic Presentations
- Exertional leg symptoms (claudication, leg pain with walking)
- Nonhealing wounds of the lower extremities
- Rest pain in the feet or legs
Age-Based Screening
- All patients ≥65 years with any suspicion of PAD
- Patients ≥50 years with history of:
- Smoking (current or former)
- Diabetes mellitus
High-Risk Asymptomatic Patients (Class IIa)
It is reasonable to order ABI in patients at increased cardiovascular risk even without symptoms, including those with 1:
- Known atherosclerotic disease in other vascular beds (coronary, carotid, renal)
- Multiple cardiovascular risk factors
- Family history of PAD
When ABI Alone Is Insufficient
Important caveat: In patients with suspected PAD but noncompressible vessels (ABI >1.40), order a toe-brachial index (TBI) instead 1. This occurs commonly in:
- Long-standing diabetes with arterial calcification
- Advanced age with vessel calcification
- Chronic kidney disease 2
The guidelines are explicit that TBI should be measured when ABI is >1.40 to avoid missing PAD diagnosis 1.
Additional Testing Scenarios
Exercise ABI Testing
Order exercise treadmill ABI when 1:
- Patient has exertional non-joint-related leg symptoms
- Resting ABI is normal (1.00-1.40) or borderline (0.91-0.99)
- You suspect PAD despite normal resting measurements
Critical Limb Ischemia Evaluation
In patients with nonhealing wounds or gangrene, use TBI with waveforms, transcutaneous oxygen pressure (TcPO2), or skin perfusion pressure (SPP) to evaluate local perfusion, particularly when 1:
- ABI is abnormal (≤0.90)
- Vessels are noncompressible (ABI >1.40 with TBI ≤0.70)
Common Pitfalls to Avoid
Do not order ABI in patients without increased PAD risk and no suggestive symptoms—this is a Class III (No Benefit) recommendation 1. The test has limited utility as a screening tool in truly low-risk populations.
Recognize ABI limitations: Studies show ABI has only 57% sensitivity for detecting ≥50% stenosis in symptomatic PAD patients, dropping to 51% in diabetics and 43% in chronic kidney disease patients 2. In symptomatic patients with normal/inconclusive ABI (43% of cases), proceed directly to duplex ultrasound imaging rather than assuming PAD is absent 2.
Age threshold evolution: Note that guidelines evolved from age ≥70 years (2005) to ≥65 years (2011) based on epidemiologic data showing 21% PAD prevalence in this population 3. The 2016 guidelines maintained this threshold 1.
Diagnostic Algorithm Summary
- First-line: Resting ABI for any patient meeting criteria above
- If ABI >1.40: Order TBI (noncompressible vessels)
- If ABI 0.91-1.40 with symptoms: Order exercise ABI
- If normal ABI but high clinical suspicion: Proceed to duplex ultrasound 1
- Report ABI results standardly: Abnormal (≤0.90), borderline (0.91-0.99), normal (1.00-1.40), or noncompressible (>1.40) 1
The evidence strongly supports using specific clinical criteria rather than broad screening, as ABI testing in low-risk asymptomatic patients lacks benefit and may lead to unnecessary downstream testing 1.