REPORTING BOTH THE HIGHEST AND LOWEST ANKLE-BRACHIAL INDEX INCREASES THE DIAGNOSTIC YIELD BY DETECTING OTHERWISE IGNORED INFRA-POPLITEAL DISEASE Author Block: M Matangi, A Thakrar, D Armstrong, A Peirce, D BrouillardKingston, Ontario Abstract:PURPOSE: The ankle-brachial index is calculated by dividing the highest of the right or left brachial systolic pressure by the highest of the two ankle pressures measured at the posterior tibial (PT) or dorsalis pedis (DP) sites. This calculation has a high sensitivity and specificity for a hemodynamicaly significant stenosis proximally in the aorto-iliac, ileo-femoral, common femoral or superficial femoral arterial regions. However, the ABI as currently reported has the potential of missing infra-popliteal disease in either the anterior tibial or posterior tibial territories. The purpose of our investigation was to determine the frequency of infra-popliteal disease in patients with a normal ABI.METHODS: PADfile, the peripheral arterial disease module of CARDIOfile, our cardiology database was searched for all patients (P) who had peripheral arterial testing (PAD). Only P who had both the anterior tibial ABI and the posterior tibial ABI recorded were included. An ABI of >0.90 was considered normal and an ABI of <0.91 was considered abnormal. Those P with a normal ABI were analyzed to see how many had an ABI of <0.91 in the lowest of the two ABIs measured for each ankle.RESULTS: A total of 2,365 lower limbs were examined that fulfilled the above criteria. Of these 397 (16.8%) had an ABI of 0.90. There were another 180 (9.1%) where the conventionally recorded ABI was >0.90 but the other ABI in either DP or PT sites was <0.91 indicating infra-popliteal disease not reflected in the conventional method of reporting the ABI.CONCLUSION: The conventional method of reporting an ABI detects hemodynamically significant proximal lower limb PAD. In P with a normal ABI there is the potential to miss infra-popliteal disease confined to either the anterior tibial or posterior tibial territories. We believe that both the highest and the lowest ABIs for each ankle should be reported, this would eliminate the potential for missing infra-popliteal PAD confined to either the anterior tibial or posterior tibial territories, thus allowing such therapy such as Aspirin, Statins and ACE Inhibitors to another 9.1% of P. :Author Disclosure Information: M. Matangi, None; A. Thakrar, None; D. Armstrong, None; A. Peirce, None; D. Brouillard, None.