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Difficulty: MediumDiagnostic Workup and Test Sequencing

A 6262-year-old man presents to the outpatient clinic reporting a 44-month history of right calf pain. He describes the pain as a severe, cramping ache that consistently begins after walking approximately two blocks. The pain forces him to stop and rest, and it completely resolves within 55 minutes of standing still. His medical history is significant for type 2 diabetes mellitus, hypertension, hyperlipidemia, and a 4040-pack-year smoking history. His current medications include metformin, lisinopril, and atorvastatin. Vital signs show a blood pressure of 145/88145/88 mmHg and a heart rate of 7878/min. On physical examination, the skin of the bilateral lower extremities is thin, shiny, and lacks hair distally. The right dorsalis pedis and posterior tibial pulses are palpable but significantly diminished compared to the left. No ulcerations or gangrene are noted. Which of the following is the most appropriate next step in the diagnostic workup?

  1. A
    Arterial duplex ultrasonography of the lower extremities
  2. B
    Computed tomography angiography of the lower extremities
  3. C
    Measurement of serum creatine kinase concentration
  4. D
    Exercise treadmill testing with electrocardiography
  5. Ankle-brachial index measurementAnswer

Answer

The most appropriate initial step in the diagnostic workup is an ankle-brachial index measurement.
This patient presents with classic symptoms of intermittent claudication and physical signs of peripheral arterial disease (PAD). According to diagnostic guidelines, the initial test of choice to objectively confirm the diagnosis of PAD is the ankle-brachial index (ABI). The ABI compares the systolic blood pressure measured at the ankle to the systolic blood pressure measured at the brachial artery. A resting ABI of ≤0.90\leq 0.90 is considered diagnostic for PAD. It is a highly sensitive, non-invasive, and inexpensive first step.

Step-by-Step Solution

1
Identify the primary clinical syndrome from the patient's history and risk factors.
The patient has exertional right calf pain relieved by rest, which is the classic presentation of intermittent claudication. He also has multiple risk factors for atherosclerosis (smoking, diabetes, hypertension, hyperlipidemia).
Recognizing the symptom pattern narrows the differential diagnosis to peripheral vascular pathology rather than musculoskeletal or neurologic causes.
2
Correlate the history with the physical examination findings.
The examination reveals diminished distal pulses, thin, shiny skin, and hair loss on the lower extremities.
These are classic signs of chronic hypoperfusion, strongly supporting a clinical diagnosis of peripheral arterial disease (PAD).
3
Determine the guideline-directed initial diagnostic test for this specific condition.
The first-line test to objectively confirm PAD is the measurement of the ankle-brachial index (ABI).
ABI is non-invasive, cost-effective, and highly sensitive. Advanced imaging (like duplex ultrasonography or CT angiography) should only be sequenced after the diagnosis is confirmed and only if invasive revascularization is being planned.

Key Concept

The initial diagnostic test of choice for suspected peripheral arterial disease (PAD) is the ankle-brachial index (ABI), not advanced anatomic imaging.
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Diagnostic Workup and Test Sequencing

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