Is it negligible to omit the Ankle-Brachial Index (ABI) from the initial workup for a patient with a significant smoking history, possible psoriatic arthritis, and foot pain?

Was Omitting ABI from Initial Workup Negligent?

Yes, omitting the ABI from the initial workup represents a significant deviation from established guidelines and constitutes negligent care for this patient with a smoking history and foot pain. 1, 2

Clear Guideline-Based Indication for ABI Testing

The ACC/AHA guidelines provide explicit Class I recommendations (highest level) that the resting ABI should be used to establish lower extremity PAD diagnosis in patients ≥50 years old with a history of smoking, regardless of symptom type. 1 This is not a "consider" recommendation—it is a "should" recommendation with Level B evidence, meaning the benefit substantially outweighs the risk. 1

Your patient's smoking history alone automatically triggers this Class I indication for ABI testing. 2 The guidelines specifically state that ABI should be performed in patients with:

• Age ≥50 years with smoking history (your patient qualifies) 1
• Age ≥65 years (regardless of other factors) 1
• Nonhealing wounds 1
• Exertional leg symptoms 1

Why This Omission Matters Clinically

Smoking is the single most important modifiable risk factor for PAD, with heavy smokers having substantially elevated risk. 2 Missing PAD diagnosis in a smoker has serious consequences:

• Patients with PAD face a 25-35% risk of myocardial infarction or stroke over 5 years, plus an additional 25% mortality rate. 2
• The ABI is 95% sensitive and specific for angiographic PAD when <0.90. 2, 3
• An abnormal ABI (<0.90) is a powerful independent marker of cardiovascular risk and all-cause mortality (relative risk 1.6 in men, 1.9 in women). 4

Critical Pitfall: Relying on Clinical Examination Alone

The presence of normal pulses does NOT reliably rule out PAD. 2 This is a common and dangerous pitfall. Palpable pulses can be present even with significant arterial disease. 2 The ABI is objective, noninvasive, simple to perform, and should be measured in both legs to establish baseline. 1, 2

The Psoriatic Arthritis Red Herring

While psoriatic arthritis commonly affects the foot and ankle (86% of cases in one series, with 55% presenting there initially), 5 this does NOT exclude concurrent vascular disease. 2 In fact, misdiagnosis is common when clinicians fail to consider multiple pathologies simultaneously. 5 The heel and midfoot pain pattern does not exclude concurrent vascular disease. 2

Algorithmic Approach That Should Have Been Followed

1. Recognize smoking history as automatic trigger: Age ≥50 + smoking = Class I indication for ABI 1, 2
2. Perform bilateral resting ABI regardless of pulse examination findings 1, 2
3. Interpret results systematically: 1
   • ABI ≤0.90 = PAD confirmed
   • ABI 0.91-0.99 = Borderline (consider exercise ABI)
   • ABI 1.00-1.40 = Normal
   • ABI >1.40 = Noncompressible vessels (obtain toe-brachial index)

Perioperative Risk Implications

The perioperative period poses particular risk for patients with undiagnosed PAD, especially when combined with immobilization and continued smoking. 2 Missing this diagnosis before any potential surgical intervention for the foot pain compounds the negligence.

Standard of Care Violation

The ABI test is simple, noninvasive, can be performed in the office setting, and has been recommended as first-line testing since at least 2005 (updated 2011). 1 There is no reasonable justification for omitting this test in a patient who clearly meets guideline criteria. The test takes minutes to perform and provides critical prognostic information beyond just diagnosing PAD. 4, 3