Should an ABI Test Be Considered for Suspected PAD?
Yes, the resting ABI test is the recommended first-line diagnostic test and should be performed in all patients with history or physical examination findings suggestive of peripheral artery disease. 1
When ABI Testing is Recommended
Class I Recommendations (Strongest Evidence)
Perform resting ABI in patients with any history or physical examination findings suggestive of PAD to establish the diagnosis, with or without ankle pulse volume recordings (PVR) and/or Doppler waveforms. 1
ABI testing is mandatory for all patients with lower extremity wounds as the first-line test to establish PAD diagnosis and guide wound management decisions. 2
Patients with exertional, nonjoint-related leg symptoms and normal or borderline resting ABI (>0.90 and ≤1.40) require exercise treadmill ABI testing to evaluate for PAD, as resting measurements may miss significant disease. 1
Class IIa Recommendations (Reasonable to Perform)
- Screening with resting ABI is reasonable in patients at increased risk of PAD, even without symptoms, including those with diabetes, smoking history, age ≥65 years, or age ≥50 years with cardiovascular risk factors. 1, 2
Diagnostic Accuracy and Interpretation
The ABI demonstrates high specificity (83-99%) and accuracy (72-89%) for detecting ≥50% stenosis, though sensitivity varies (15-79%), particularly in elderly patients and those with diabetes. 3 The test has been validated against imaging methods with areas under the ROC curve of 0.87-0.95 for Doppler-based measurements. 4
Standard ABI Interpretation Categories 1, 5:
- Abnormal: ABI ≤0.90 (confirms PAD diagnosis)
- Borderline: ABI 0.91-0.99 (requires exercise testing if symptomatic)
- Normal: ABI 1.00-1.40
- Noncompressible: ABI >1.40 (requires alternative testing)
When ABI is NOT Appropriate
Do not perform ABI screening in patients without risk factors for PAD and without suggestive history or physical examination findings, as PAD prevalence is very low (approximately 1%) in this population and testing provides no benefit. 1, 5
Critical Limitations and Required Alternative Testing
When ABI >1.40 (Noncompressible Vessels)
ABI is unreliable in patients with arterial calcification (common in diabetes and advanced chronic kidney disease), requiring mandatory alternative testing. 1, 5
Perform toe-brachial index (TBI) with waveforms when ABI >1.40, as this is the recommended first-line alternative test. 1, 5 A TBI <0.70 confirms PAD diagnosis. 5
For Wound Assessment
ABI alone is insufficient for evaluating lower extremity wounds, as it may be normal in nearly 25% of patients with chronic limb-threatening ischemia, and 29% of such patients have ABI between 0.70-1.40. 2 The concordance between ABI and toe pressure is poor, with only 58% of patients meeting criteria for abnormal toe pressures presenting with abnormal ABIs. 2
For all lower extremity wounds, perform comprehensive vascular assessment including: 2
- ABI measurement as first-line test
- TBI measurements, especially when ABI is normal or elevated
- Transcutaneous oxygen pressure (TcPO2) and/or skin perfusion pressure (SPP) to predict wound healing potential (TcPO2 >30 mm Hg or SPP >40 mm Hg predicts healing)
Common Pitfalls and How to Avoid Them
Relying solely on ABI may miss significant arterial disease in patients with diabetes or advanced age due to arterial calcification causing falsely elevated readings. 2, 5 Always proceed to TBI testing when ABI >1.40.
Proper training is essential for accurate ABI measurement. Didactic learning alone is insufficient—combining didactic with experiential learning significantly improves proficiency in performing the procedure correctly. 6
Perform perfusion assessments in a warm room to prevent arterial vasoconstriction from cold exposure, which leads to inaccurate results. 2
The method of calculating ABI significantly affects PAD prevalence estimates, with differences corresponding to approximately 2.2 million persons who would be reclassified. 7 Use standardized reporting as recommended by guidelines.