Factors affecting the validity of ankle-brachial index in the diagnosis of peripheral arterial obstructive disease.

We evaluated 158 legs from 79 consecutive patients who had undergone both ankle-brachial index (ABI) measurements and angiography for claudication symptoms between January 2007 and December 2008. The diagnosis of peripheral arterial disease (PAD) in the individual legs was established by angiography. Ankle-brachial index was considered abnormal if it was <0.9. The sensitivity and specificity of ABI was 61% and 87%, respectively. To assess the factors affecting the validity of ABI in the diagnosis of PAD, multivariate logistic regression analysis was conducted. The odds ratios (ORs) for the false negative result of ABI were 4.36 (95% confidence interval [CI] 1.36-13.92) in patients with diabetes mellitus (DM), 3.41 (95% CI 1.10-10.48) in patients with distal lesions, 3.02 (95% CI 1.07-8.49) in elderly patients, and 1.13 (95% CI 0.34-3.42) in patients with mild stenosis. Although ABI is the method of choice for the primary diagnosis of PAD, other supplementary investigations should be considered when there is clinical suspicion of PAD but an ABI <0.9.