Measure systolic blood pressure in both brachial arteries and both ankle arteries
Use the higher brachial systolic pressure as the denominator
For each leg, use the higher ankle systolic pressure from the dorsalis pedis or posterior tibial artery as the numerator
Calculate ABI for each leg using: ABI = ankle systolic pressure รท higher brachial systolic pressure
Record the result separately for the right and left leg
If needed, calculate toe-brachial index when ankle arteries are noncompressible or ABI is unreliable