Should PAD have been suspected in a smoker with possible psoriatic arthritis and intermittent foot pain that later progressed to limb-threatening ischemia post-back surgery?

Should PAD Have Been Suspected and ABI Ordered?

Yes, you should have suspected PAD as a differential diagnosis and ordered an ABI in this patient with a 40 pack-year smoking history presenting with foot pain, and the failure to do so represents a missed opportunity for early diagnosis and risk stratification.

Why PAD Should Have Been on Your Differential

The ACC/AHA guidelines are explicit about when to suspect PAD and order ABI testing:

• The resting ABI should be used to establish lower extremity PAD diagnosis in patients ≥50 years old with a history of smoking or diabetes 1
• Your patient met clear criteria: active smoker with ~40 pack-year history, which is one of the most significant risk factors for PAD 1
• Smoking is the single most important modifiable risk factor for PAD, with heavy smokers having substantially elevated risk 1, 2

The Clinical Presentation Was Atypical But Concerning

The foot presentation you describe had features that should have raised suspicion:

• Only 10-11% of PAD patients present with classic intermittent claudication 3, 4
• 50% of PAD patients have atypical leg symptoms, and 40% have no leg symptoms at all 4
• Warm, red foot with pain could represent inflammatory arthritis (as you suspected), but the presence of normal pulses does NOT reliably rule out PAD 1
• The heel and midfoot pain pattern, while consistent with psoriatic arthritis, does not exclude concurrent vascular disease 1

The Missed Diagnostic Opportunity

A simple ABI measurement would have identified PAD in this high-risk patient:

• ABI testing is 95% sensitive and specific for angiographic PAD when <0.90 1
• The test is simple, noninvasive, and should be performed in both legs to establish baseline 1
• In the PARTNERS study, 29% of at-risk primary care patients had PAD, with 55% being newly diagnosed 3
• Among newly diagnosed PAD patients, only 49% of physicians were aware of the diagnosis, highlighting how commonly it is missed 3

The Consequences of Missed Diagnosis

Your patient's progression to limb-threatening ischemia post-surgery illustrates the critical importance of early detection:

• Patients with PAD have a 25-35% risk of myocardial infarction or stroke over 5 years, with an additional 25% mortality rate 1
• Undiagnosed PAD patients receive less intensive treatment for risk factors and are prescribed antiplatelet therapy less frequently than those with known cardiovascular disease 3
• The perioperative period poses particular risk for patients with undiagnosed PAD, especially when combined with immobilization and continued smoking 1

What Should Have Been Done

The algorithmic approach for this patient should have been:

1. Recognize smoking history as automatic trigger for ABI testing (≥50 years old + smoking history = Class I indication) 1
2. Perform bilateral resting ABI regardless of pulse examination findings 1
3. If ABI ≤0.90: Confirm PAD diagnosis 1, 5
4. If ABI 0.91-0.99: Consider borderline, may need exercise ABI 5
5. If ABI >1.40: Obtain toe-brachial index due to noncompressible vessels 1, 5
6. Initiate aggressive risk factor modification: smoking cessation, antiplatelet therapy, statin, ACE inhibitor 3, 4, 2

Critical Pitfalls to Avoid

• Never rely on palpable pulses alone to exclude PAD - pulses can be normal even with significant disease 1
• Don't assume atypical symptoms exclude PAD - most PAD patients don't have classic claudication 3, 4
• Don't wait for symptoms to worsen - early detection allows for preventive interventions 3
• Don't underestimate smoking as a risk factor - it's the most potent modifiable risk factor for PAD 1, 2

The Bottom Line for Future Practice

For any patient ≥50 years old with smoking history presenting with any lower extremity symptoms, order an ABI 1. The test takes minutes, costs little, and the consequences of missing PAD—as your patient's case demonstrates—can be catastrophic 1, 3. The warm, red foot may have been psoriatic arthritis, but the smoking history alone mandated vascular assessment regardless of the presumed inflammatory etiology 1.