Association Between Intradialytic Foot Temperature Gradients and Severe Peripheral Artery Disease in Patients Undergoing Hemodialysis: Prospective Cohort Study.

Background: Peripheral artery disease (PAD) is prevalent in hemodialysis (HD) patients but remains difficult to diagnose due to unreliable ankle-brachial index (ABI) measurements caused by vascular calcification. We hypothesized that monitoring foot temperatures and their changes during HD, provoked by hemodynamic shifts, could serve as a novel diagnostic tool for detecting severe PAD. Objective: This study aims to evaluate the diagnostic utility of intradialytic foot temperature monitoring using wearable mobile health (mHealth) sensors for detecting severe PAD in patients undergoing HD. Methods: In this prospective observational study, we recruited 109 patients undergoing chronic maintenance HD. Skin temperatures were monitored continuously at the instep and sole during HD sessions using wearable sensors (Temp Pal, iWEECARE Co, Ltd), which are wireless, nanochip-based mHealth thermometers with ±0.05 °C accuracy. The diagnostic performance of temperature parameters, specifically the temperature difference between the wrist and foot at the end of HD, was evaluated against vascular duplex ultrasound (DUS). Severe PAD was defined as abnormal (monophasic or absent) flow in the distal posterior tibial artery (PTA) or anterior tibial artery (ATA). Results: Patients with abnormal tibial flow on DUS exhibited significantly different temperature gradients between the wrist and foot at the end of dialysis compared to those with normal flow. Receiver operating characteristic (ROC) analysis demonstrated that the wrist-foot temperature difference at the sole effectively discriminated abnormal ATA flow (area under the curve [AUC] 64.5%, 95% CI 57.8%-70.9%) and abnormal PTA flow (AUC 62.0%, 95% CI 55.2%-68.5%). Notably, an instep wrist-foot temperature difference cutoff of -2.2 °C or less yielded a specificity of 97.6% (95% CI 94.0%-99.3%) for detecting abnormal PTA flow. Conclusions: Intradialytic foot temperature monitoring, particularly the temperature gradient between the wrist and foot, significantly correlates with severe tibial artery flow abnormalities. This method offers an accessible, noninvasive screening adjunct to the ABI for detecting severe PAD in the HD population. These findings indicate an association rather than a standalone diagnostic test; given the modest discriminative ability, external validation is warranted.