Clinical meaning
Peripheral arterial disease (PAD) results from atherosclerotic stenosis or occlusion of arteries supplying the lower extremities. The ankle-brachial index (ABI) is the primary diagnostic tool: systolic blood pressure at the ankle divided by systolic blood pressure at the brachial artery. Normal ABI is 1.0-1.4; ABI <0.9 confirms PAD (sensitivity 95%, specificity 99%); ABI 0.4-0.9 indicates moderate disease; ABI <0.4 indicates severe PAD with rest pain risk. ABI >1.4 suggests non-compressible calcified arteries (common in diabetes and ESRD) requiring toe-brachial index (TBI) instead (TBI <0.7 is diagnostic). The Edinburgh Claudication Questionnaire standardizes symptom assessment: intermittent claudication is calf pain with walking that resolves within 10 minutes of rest, does not occur at rest, and does not occur when standing still. Rutherford classification stages PAD severity: 0 (asymptomatic), 1-3 (mild to severe claudication), 4 (rest pain), 5-6 (tissue loss). Critical limb ischemia (CLI) is defined by rest pain >2 weeks, non-healing ulcers, or gangrene with ABI <0.4 or ankle pressure <50 mmHg — CLI requires urgent vascular referral. The NP screens for PAD in high-risk populations: age >65, age 50-64 with risk factors, and any patient with exertional leg symptoms.