Next Step: Obtain Ankle-Brachial Index (ABI) Testing
The next step is to obtain a resting ankle-brachial index (ABI) with or without segmental pressures and waveforms to establish or exclude peripheral artery disease (PAD). 1, 2, 3
Why ABI Testing is Mandatory
This patient's presentation—bilateral leg pain gradually worsening over 3 months, reduced outdoor activity, and fatigue with short-distance walking—is highly suggestive of PAD, even without classic intermittent claudication. 2, 3
Most PAD patients do not present with typical claudication: Only 13-19% have classic symptoms, while 46-62% have atypical leg pain and 26-48% are labeled "asymptomatic" but have measurable functional impairment. 1, 2, 3
Normal physical examination does not exclude PAD: Up to 50% of PAD patients are asymptomatic, and 70% lack classic claudication symptoms. 1, 3
The recent decrease in outdoor activities is a critical red flag: PAD patients characteristically become sedentary and self-limit walking due to discomfort, which matches this patient's presentation. 2, 3
How to Interpret ABI Results
The ABI should be reported and acted upon as follows: 1, 2
- ABI ≤0.90: Abnormal—diagnostic of PAD
- ABI 0.91-0.99: Borderline—requires exercise treadmill ABI testing
- ABI 1.00-1.40: Normal—but if symptoms persist, perform exercise treadmill ABI testing
- ABI >1.40: Noncompressible vessels—proceed to toe-brachial index (TBI) testing
Critical Next Steps Based on ABI Results
If ABI is normal or borderline (>0.90) but symptoms persist: Exercise treadmill ABI testing is mandatory to objectively measure functional limitation and diagnose PAD, as nearly half of symptomatic patients have normal resting ABI. 1, 2, 4
If ABI is abnormal (≤0.90): 1
- Initiate cardiovascular risk reduction immediately (antiplatelet therapy, high-intensity statin, blood pressure control, smoking cessation)
- Consider exercise treadmill testing to objectively assess functional status
- Obtain duplex ultrasound to assess anatomic disease severity and guide management
If ABI is >1.40 (noncompressible): Measure TBI, as this indicates medial arterial calcification common in diabetes and chronic kidney disease. 1, 2
Why This Cannot Wait
PAD is a marker of systemic atherosclerosis with dramatically increased cardiovascular mortality: All-cause mortality is 3.1 times greater and cardiovascular mortality is 5.9 times greater compared to patients without PAD. 1
Even "asymptomatic" PAD patients have similar cardiovascular event risk as those with claudication: The 10-year cardiovascular event rate is equivalent regardless of symptom severity. 1, 3
Resting ABI alone misses 31% of PAD cases in symptomatic patients: Exercise testing is essential when resting ABI is normal but symptoms suggest PAD. 4
Common Pitfalls to Avoid
Do not assume normal examination excludes PAD: Pulse examination has limited sensitivity and specificity, and the presence of all four pedal pulses does not rule out significant disease. 2, 3
Do not delay testing based on "atypical" symptoms: The broad spectrum of PAD presentations includes atypical exertional leg pain, leg fatigue, and even absence of pain in inactive individuals. 2, 3
Do not rely on ABI alone in high-risk patients: If clinical suspicion remains high despite normal ABI, proceed directly to exercise testing or duplex ultrasound, as ABI sensitivity ranges from only 15-79% depending on disease severity and patient characteristics. 5, 4