Evaluating the Lower Extremities for Peripheral Arterial Obstructive Disease Using the Transfer Function Index

Abstract

We have evaluated the performance of pulse volume recording waveform averaging and the resulting transfer function index (TFI). The purpose of this study was to develop and validate diagnostic criteria for the use of TFI as a tool for the evaluation of patients with peripheral arterial obstructive disease (PAOD). The study prospectively evaluated 146 limbs for PAOD using previously validated criteria for conventional indirect testing and duplex ultrasound imaging and then correlated TFI measurements at multiple levels of each extremity. Of the 146 limbs evaluated, 61 were classified as having no hemodynamically significant disease, 46 as having mild to moderate disease, and the remaining 39 categorized as severely diseased. The mean value of the TFI for each category was 1.05 (±0.15) for limbs categorized as normal, 0.86 (±0.07) for limbs categorized as mild to moderate, and 0.76 (±0.06) for limbs categorized as severe (p < 0.001). The receiver operator characteristic curve showed that the best cutoff to differentiate between normal and abnormal limbs was a TFI of 0.94, with a sensitivity of 92% and a specificity of 90%. We conclude that the TFI could effectively be used for rapid and objective evaluation of patients for the presence of PAOD.