Have the patient rest supine for at least 5 minutes
Measure systolic blood pressure in both brachial arteries
Measure systolic blood pressure in both ankle arteries: dorsalis pedis and posterior tibial
For each leg, use the higher ankle systolic pressure
Use the higher of the two brachial systolic pressures as the denominator
Calculate ABI for each leg using: ABI = higher ankle systolic pressure ÷ higher brachial systolic pressure
Repeat for the other leg
Record each leg’s ABI separately
Interpret values as:
ABI 1.00 to 1.40: normal
ABI 0.91 to 0.99: borderline
ABI 0.41 to 0.90: mild to moderate peripheral artery disease
ABI 0.00 to 0.40: severe peripheral artery disease
ABI greater than 1.40: noncompressible arteries