Diagnostic utility of the two methods of ankle brachial index in the detection of peripheral arterial disease of lower extremities

Abstract

Background: Peripheral arterial disease (PAD) is a common disease that is diagnosed with a screening test called the Ankle Brachial Index (ABI). Different methods of ABI have been described in the literature. We wanted to estimate and compare the sensitivity and specificity of an alternative method of calculating the ABI (LAP ABI, low ankle pressure ABI) with the current method (named high ankle pressure (HAP)), using digital subtraction angiography (DSA) as the gold standard.

Methods: We reviewed the records of all patients who had undergone DSA at a major academic center between August 2003 and October 2005. The study includes 107 patients/208 limbs. Inclusion criteria included patients with an ABI performed within 30 days prior to the DSA. Patients with non-compressible vessels and ABI >1.40 were excluded. Abnormal ABI was defined as < or = 0.9 for both methods. Disease on angiogram was defined as the presence of 50% or more stenosis of any lower extremity artery from the aorto-iliac bifurcation to the ankle arteries.

Results: The sensitivity of the HAP and LAP ABI for the diagnosis of PAD was 69 and 84%, respectively (P < 0.001). The specificity of the HAP and the LAP method was 83 and 64% respectively (P < 0.01). The overall accuracy of LAP ABI and HAP ABI was 80 and 72%, respectively.

Conclusions: The LAP ABI has better sensitivity and overall accuracy in comparison to the HAP ABI to diagnose PAD.