Efficacy of the transfer function index using the pulse volume recording as a parameter to assess intermittent claudication

Purpose  The aim of this study was to elucidate whether the ankle brachial pressure index (ABPI) or transfer function index (TFI) was useful as an alternative parameter to the treadmill-walking test using near-infrared spectroscopy (NIRS) in evaluating muscle ischemia for patients with intermittent claudication (IC). Methods  In 155 claudicants, the treadmill-walking test using NIRS was performed to calculate the recovery ability index (=recovery time/walking time). The ABPI and TFI were measured at the calf (TFI_calf) and ankle (TFI_ankle) using pulse volume recording. The area under the curve (AUC) was calculated from the receiver operating characteristic (ROC) curve and cutoff value was determined using crossing point of the ROC curve with a diagonal line. Results  In the nondiabetics, AUCs were 77.3%, 80.0%, and 76.0% in the ABPI, TFI_calf, and TFI_ankle, respectively, which were not different significantly. In the diabetics, the AUC of TFI_calf was 77.9%, which was different significantly from those of the other indices such as the ABPI or TFI_ankle showing 66.2% or 68.1%. The cutoff value of ABPI indicating moderate or severe IC was 0.75 in the nondiabetics whereas that of TFI_calf was 0.85 in the diabetics. Conclusion  TFI_calf was useful to distinguish moderate or severe IC from mild IC in diabetic patients even if the ABPI was sufficient in nondiabetic patients.