Additional prognostic value of toe-brachial index beyond ankle-brachial index in hemodialysis patients

Abstract

Abstract Background Ankle-brachial index (ABI), the first-line diagnostic test for peripheral artery disease, can be falsely elevated when ankle arteries are incompressible, showing a J-shaped association with mortality. In this situation, toe-brachial index (TBI) is the recommended test. However, whether TBI provides additional prognostic information beyond ABI in patients on hemodialysis is unknown. Methods In this retrospective cohort study of 247 Japanese prevalent hemodialysis patients (mean age 66.8 [SD 11.6] years), we evaluated mortality (116 deaths over a median follow-up of 5.2 years) related to quartiles of ABI and TBI, as well as three categories of low ABI (≤0.9), normal/high ABI (> 0.9) + low TBI (≤0.6), and normal/high ABI + normal TBI (> 0.6) using multivariable Cox models. Results ABI showed a J-shaped association with mortality (adjusted hazard ratio 2.72 [95% CI, 1.52–4.88] in the lowest quartile and 1.59 [95% CI, 0.87–2.90] in the highest quartile vs. the second highest). Lower TBI showed a potentially dose-response association with mortality (e.g., adjusted hazard ratios 2.63 [95% CI, 1.36–5.12] and 2.89 [95% CI, 1.49–5.61] in the lowest two quartiles vs. the highest). When three categories by both ABI and TBI were analyzed, those with low ABI (≤0.9) experienced the highest risk followed by normal/high ABI (> 0.9) + low TBI (≤0.6). Among patients with normal/high ABI (> 0.9), the increased mortality risk in individuals with low TBI (≤0.6) compared to those with normal TBI (> 0.6) were significant (adjusted hazard ratio 1.84 [95% CI, 1.12–3.02]). Conclusions Lower TBI was independently associated with mortality in patients on hemodialysis and has the potential to classify mortality risk in patients with normal/high ABI. Our results support the importance of evaluating TBI in addition to ABI in this clinical population.