Aims: The ankle-brachial index is an efficient tool for objectively documenting the presence of lower extremity peripheral artery disease. However, its applicability for detection of critical leg ischemia is still controversial. We proposed to determine the diagnostic accuracy of the ankle-brachial index for critical ischemia.
Materials and methods: Systolic blood pressure measurements for calculation of the ankle-brachial index were obtained in 90 patients with peripheral artery disease. Ankle-brachial index was computed in 3 different ways (using the lowest ankle pressure, the highest ankle pressure, and the mean of the ankle pressures), sensibility, specificity, positive and negative predictive value and overall accuracy for detecting critical ischemia were determined for each method. A value ≤ 0.4 was taken as cut-off point for critical leg ischemia. Prevalence of coronary and cerebrovascular atherosclerosis and conventional risk factors were also noted.
Results: Using the lowest ankle pressure for computing ankle-brachial index provided higher sensitivity, and lower specificity for detecting critical leg ischemia, using the highest pressure was less sensitive, but more specific, and the mean pressure index gave intermediate results. Overall accuracy was highest for the latest method. The prevalence of generalized atherosclerosis was high in peripheral artery disease, but we found no significant difference between the intermittent claudication and the critical ischemia group.
Conclusion: Ankle-brachial index measurements, regardless of the method used for calculation, cannot identify or rule out reliably critical leg ischemia. Peripheral artery disease confers an increased risk of cardiovascular disease regardless of symptom status or lower extremity perfusion severity.