Does a normal ankle-brachial index (ABI) exclude peripheral artery disease (PAD) claudication in patients?

Does a Normal ABI Exclude PAD Claudication?

No, a normal resting ankle-brachial index (ABI) does NOT reliably exclude peripheral artery disease (PAD) causing claudication, and patients with exertional leg symptoms require exercise ABI testing even when resting ABI is normal or borderline (0.91-1.40). 1

Why Resting ABI Fails to Exclude PAD

Sensitivity Limitations in Symptomatic Patients

• In symptomatic patients with PAD confirmed by duplex ultrasound, 43% had normal or inconclusive resting ABI values, demonstrating that nearly half of patients with actual arterial disease are missed by resting ABI alone 2

• The sensitivity of resting ABI for detecting ≥50% stenosis is only 57% overall, dropping to 51% in diabetic patients and 43% in those with chronic kidney disease 2

• Among 396 symptomatic patients referred for vascular evaluation, 46% had normal resting ABI despite clinical suspicion warranting referral 3

Exercise Testing Unmasks Occult Disease

• ACC/AHA guidelines explicitly recommend exercise treadmill ABI testing for patients with exertional non-joint-related leg symptoms and normal or borderline resting ABI (>0.90 and ≤1.40) 1

• Of 84 symptomatic patients with normal resting ABI who underwent exercise testing, 31% had their ABI fall below 0.9 after exercise, confirming hemodynamically significant PAD 3

• A drop in ABI of ≥0.15 after exercise, or a post-exercise ankle pressure decrease >30 mmHg, is diagnostic for at least moderate arterial occlusive disease even when resting ABI is normal 1, 4

Isolated Aortoiliac Disease

• Patients with isolated iliac artery occlusive disease may have normal resting ABI because collateral flow maintains ankle pressures at rest 1

• Exercise ABI is specifically recommended to objectively evaluate functional limitations in patients suspected of PAD with isolated aortoiliac disease 1

Clinical Algorithm for Patients with Suspected Claudication

Step 1: Initial Assessment

• Measure resting ABI after 10 minutes of supine rest 1
• Interpret as: abnormal (≤0.90), borderline (0.91-0.99), normal (1.00-1.40), or noncompressible (>1.40) 1

Step 2: If Resting ABI is Normal or Borderline (0.91-1.40)

• Proceed immediately to exercise treadmill ABI testing if patient has exertional leg symptoms 1
• Do not assume PAD is excluded based on normal resting ABI alone 4, 5

Step 3: If Resting ABI is >1.40 (Noncompressible)

• Measure toe-brachial index (TBI); values <0.70-0.75 confirm PAD 1, 5
• Consider pulse volume recordings or Doppler waveform analysis 1

Step 4: If Exercise ABI is Positive

• Duplex ultrasound, CTA, or MRA to localize disease and plan revascularization if symptoms warrant intervention 1

Common Pitfalls to Avoid

Never Rely on Resting ABI Alone in Symptomatic Patients

• Even skilled examiners can detect pulses despite significant ischemia; palpable pulses do not exclude PAD 4

• Clinical examination sensitivity is too low to rule out PAD—objective testing with exercise ABI is mandatory when symptoms suggest claudication 4

Arterial Calcification Creates False Negatives

• Medial arterial calcification (Mönckeberg sclerosis) can produce falsely normal ABI readings despite significant stenotic disease, particularly in diabetic patients 4, 2

• Up to 50% of patients with ABI >1.40 have coexisting PAD despite the elevated reading 5

Diabetic and CKD Patients Require Extra Vigilance

• Diabetic patients with neuropathy often lack typical claudication symptoms even with severe PAD, making exercise testing even more critical 4

• In chronic kidney disease patients, resting ABI sensitivity drops to 43%, with overall accuracy of only 67% 2

Special Considerations

When Normal Exercise ABI Truly Excludes PAD

• Triphasic pedal Doppler arterial waveforms strongly exclude PAD 4

• TBI ≥0.75 largely excludes PAD 4

• These findings provide reassurance that symptoms have non-vascular etiology

Cardiovascular Risk Implications

• Even when PAD is excluded, an abnormal ABI (<0.90 or >1.40) identifies patients at very high cardiovascular risk requiring aggressive risk factor modification 4

• All patients with confirmed PAD require smoking cessation, statin therapy, low-dose aspirin or clopidogrel, blood pressure control, and diabetes management 4