Doppler ankle pressure: an evaluation of three methods of expression.

We studied 133 patients with arteriographic evidence of lower limb arterial disease and 34 normal volunteers to determine the most useful means of expressing ankle pressure. Representative ranges were determined for each of six symptomatic categories. Receiver operating characteristic curve analysis showed that ankle index (ankle to brachial pressure ratio) and brachial-ankle pressure gradient were more valuable than absolute pressure in discriminating between normal and disease extremities. In contrast, absolute ankle pressure was the best predictor of nonviability (limb requiring bypass for salvage or amputation). An absolute pressure cutoff of 6mm Hg correctly identified 86% of viable limbs and 77% of nonviable limbs. Thus, the diagnostic accuracy of the three methods of expressing ankle pressure depends on the context in which they are to be used, and it appears that ankle index and gradient are most appropriate for defining the presence of disease, while absolute pressure correlates best with viability.