Calculation of the ankle brachial index.

Dear Editor, We would like to call the readers’ attention to a brief communication published in the issue of January 2012, which concluded increased prevalence of left ventricular hypertrophy in subjects with an abnormal ankle brachial index (ABI). In their study, Albuquerque et al.1 compared subjects with arterial hypertension with and without an abnormal ABI. Since the prevalence of a low ABI was found to be 10.5 in a large survey conducted in Brazil2, identification and characterization of the subjects with a low or high ABI are of utmost importance. However, use of ABI in research and in clinical practice requires full adherence to guidelines. In this context, the ABI calculation technique recommended by the guideline is not in accordance with the one used in the study by Albuquerque et al.1. The authors used the mean of the two readings taken in an ankle to calculate the ABI for the respective limb. However, right or left ABI should be determined by taking the highest of the pedal pulses, either dorsalis pedis artery or posterior tibial artery, in each ankle (not the mean) as the numerator in the formula. Thus, the lowest of the calculated right and left ABIs should be recorded as the final ABI of the patient. When the mean value is used, the value of the numerator decreases, which results in the detection of a higher number of subjects with a low ABI. This is actually the technique recommended by both ACC/AHA 2005 practice guidelines for the management of patients with peripheral arterial disease (PAD)3 and the Inter-Society Consensus for the Management of PAD guideline (TASC II)4. Moreover, this issue is one of the reasons why assessment of ABI by automated oscillometric devices cannot fully replicate the classical Doppler technique5.