For Peripheral Artery Disease (PAD), which is better, Ankle-Brachial Index (ABI) or Doppler (ultrasound)?

ABI is Superior to Doppler Ultrasound for Initial PAD Diagnosis

The ankle-brachial index (ABI) is recommended as the first-line noninvasive test for screening and diagnosis of peripheral arterial disease (PAD), with Doppler ultrasound serving as a complementary tool for anatomical characterization of lesions. 1

Diagnostic Accuracy of ABI

• ABI is a low-cost, easy-to-use tool with excellent diagnostic performance for PAD, with sensitivity ranging from 68% to 84% and specificity from 84% to 99% when using the Doppler method 1
• The resting ABI has been validated as a first-line test against various imaging methods, with areas under the ROC curve of 0.87-0.95 for Doppler-based ABI measurements 1
• ABI results should be standardized and reported as: abnormal (≤0.90), borderline (0.91-0.99), normal (1.00-1.40), or noncompressible (>1.40) 1

When to Use Doppler Ultrasound

• Duplex ultrasound is indicated as a first-line imaging method to confirm PAD lesions after ABI screening has been performed 1
• Doppler ultrasound is particularly valuable for anatomical characterization of PAD lesions and guidance for optimal revascularization strategy 1
• In cases of noncompressible arteries (ABI >1.40), alternative methods such as Doppler waveform analysis or pulse volume recording are indicated 1

Special Considerations

• For patients with incompressible ankle arteries (common in diabetes and advanced chronic kidney disease), toe-brachial index (TBI) should be measured instead of ABI 1
• In patients with exertional limb pain but normal or borderline resting ABI (>0.90 and ≤1.40), exercise treadmill ABI testing should be performed to evaluate for PAD 1
• Both European and American guidelines agree that ABI is the initial test of choice, with Doppler ultrasound serving as a secondary diagnostic tool 1

Recent Innovations

• Recent research has explored simplified ABI measurement techniques using Doppler waveform classification, showing excellent concordance with standard ABI measurement methods 2
• Semi-automatic oscillometric ABI measurements have shown comparable diagnostic results to conventional Doppler methods, with potential time savings of about 5 minutes per examination 3
• Cuffless Doppler-based estimated ABI has shown promise in recent studies, particularly for patients with media sclerosis (including those with diabetes) 4

Common Pitfalls

• Despite being recommended as a grade 1, level A evidence test, ABI is underutilized in clinical practice, with one study showing only 22.5% of patients had ABI measured both before and after peripheral vascular intervention 5
• Lack of standardization in ABI measurement techniques and cutoff points for abnormal ABI can lead to inconsistent results 6
• Proper training improves reproducibility of ABI measurements, with experienced physicians achieving better results 1

In conclusion, while both ABI and Doppler ultrasound are valuable tools in PAD diagnosis, current guidelines from both European and American cardiology societies clearly position ABI as the initial diagnostic test, with Doppler ultrasound serving as a complementary imaging method for anatomical characterization and revascularization planning.