What initial tests should be done for a patient, likely an adult with potential risk factors such as smoking, diabetes (Diabetes Mellitus), or hypertension, presenting with circulation issues in the left foot, nocturnal calf aches, and cold big toes?

Initial Diagnostic Workup for Left Foot Circulation Issues with Nocturnal Calf Pain and Cold Toes

Begin with ankle-brachial index (ABI) measurement as the primary screening test, followed by comprehensive foot examination including pedal pulse assessment, neurological testing with 10-g monofilament, and vascular assessment—this combination establishes both the presence and severity of peripheral arterial disease while ruling out neuropathic causes. 1

Immediate Clinical Assessment

History Taking

• Document claudication characteristics: Ask specifically about walking distance before pain onset, whether pain resolves with rest, and if symptoms are reproducible with similar exertion levels 1, 2
• Assess cardiovascular risk factors: Record smoking history, diabetes status, hypertension, hyperlipidemia, and duration of diabetes if present (>10 years increases PAD risk) 1
• Identify red flags: Previous foot ulceration, amputation history, visual impairment, and current tobacco use all elevate risk for complications 1

Physical Examination Components

• Vascular assessment: Palpate dorsalis pedis and posterior tibial pulses bilaterally; inspect for skin integrity, color changes, and temperature differences between limbs 1
• Neurological examination: Perform 10-g monofilament testing plus one additional test (pinprick, vibration with 128-Hz tuning fork, or ankle reflexes) to identify loss of protective sensation (LOPS) 1
• Skin inspection: Look for erythema, warmth, calluses, ulcers, or gangrene in a well-lit room 1

Primary Diagnostic Tests

Ankle-Brachial Index (ABI)

The ABI should be performed as the initial objective test in all patients over 50 years with claudication symptoms or in younger patients with diabetes plus one additional atherosclerosis risk factor. 1, 3

• Interpretation: ABI ≤0.90 confirms PAD; values 0.41-0.90 indicate mild-to-moderate disease; ≤0.40 suggests severe ischemia 1, 3
• Important caveat: ABI may be falsely elevated or normal in patients with heavily calcified vessels (common in diabetes) or isolated iliac disease 1
• If ABI is normal but symptoms persist: Proceed to exercise/treadmill ABI testing to unmask functional limitations from aortoiliac disease 1

Duplex Ultrasound of Lower Extremities

Order duplex Doppler ultrasound to localize anatomic segments of disease and assess stenosis severity. 1, 3

• Accuracy: 92% sensitivity and 96% specificity for detecting significant aortoiliac lesions when compared to angiography 1
• Advantages: Non-invasive, no contrast exposure, can be performed simultaneously with ABI 1

Secondary/Advanced Testing (When Initial Tests Are Positive)

CT Angiography (CTA) with Runoff

If ABI is abnormal (<0.90) or duplex shows significant stenosis, obtain CTA of abdomen/pelvis with bilateral lower extremity runoff to define anatomy for revascularization planning. 1

• Indications: Moderate recommendation from ACC/AHA for determining anatomic disease location and stenosis significance before intervention 1
• Benefits: Allows precise surgical/endovascular planning, potentially reduces contrast dose during actual procedures 1
• Alternative: MRA with IV contrast (rating 7) if contrast load is a concern, though CTA is generally preferred 1

Risk Stratification and Referral Criteria

When to Refer for Vascular Assessment

Refer immediately to vascular surgery if any of the following are present: 1, 3

• Symptoms of claudication with decreased or absent pedal pulses 1
• Positive ABI (<0.90) with significant symptoms 1
• Ischemic rest pain (pain at rest in lower leg/foot, worse when recumbent) 1
• Non-healing wounds or tissue loss 1
• ABI <0.40 indicating severe ischemia 3

Diabetes-Specific Considerations

In diabetic patients, perform comprehensive foot examination at every visit if there is evidence of sensory loss or prior ulceration. 1

• Screen with ABI in diabetic patients over 50 years, or under 50 with additional PAD risk factors (smoking, hypertension, hyperlipidemia, diabetes duration >10 years) 1
• Recognize that diabetic neuropathy can coexist with PAD—the combination dramatically increases amputation risk 1

Critical Pitfalls to Avoid

• Do not rely on pulse examination alone: Sensitivity and specificity are limited; objective vascular testing with ABI is mandatory 1
• Do not dismiss normal resting ABI in symptomatic patients: Isolated iliac disease may show normal resting ABI—exercise testing is required 1
• Do not overlook calcified vessels: In patients with diabetes or renal disease, non-compressible vessels yield falsely elevated ABI; obtain toe-brachial index instead 1
• Do not delay referral for severe symptoms: Rest pain, tissue loss, or ABI <0.40 require urgent vascular consultation within 24 hours 3, 4

Concurrent Laboratory Testing

• Lipid profile: Total cholesterol, LDL-C, HDL-C, triglycerides (target LDL-C <55 mg/dL in PAD patients) 3
• Hemoglobin A1c: If diabetes suspected or known (target <7%) 3
• Renal function: Baseline creatinine before contrast studies 1