Toe- Brachial Index: Utility, Futility, and Diagnostic Criteria

Ankle brachial index (ABI) can be unreliable in patients with non-compressible vessels. Our aim is to determine the feasibility of toe brachial index (TBI) and reporting criteria in a large population. We evaluated Doppler waveforms and segmental pressures in 26,719 limbs. TBI was obtained in 92.7%, mean TBI = 0.61 ± 0.25. TBI was obtained in 82%of limbs with unobtainable ABI. In hemodynamically normal subgroup (defined as those with normal ankle-brachial indices at rest and after exercise) the mean TBI was 0.84 ± 0.14. In severe PAD subgroup (defined as ABI < 0.5 and monophasic waveforms) the mean TBI was 0.16 ± 0.12. Limbs with a diagnosis of a PAD (ABI ≤ 0.9) had a TBI <0.8 in 99.5% of the cases, and <0.6 in 90% of the cases. A TBI of 0.8 had a negative predictive value for PAD of 0.99. A TBI cutoff of 0.6 had a positive predictive value for PAD of 0.95. Based on these results we propose defining normal TBI above 0.8, borderline between 0.8 and 0.61, abnormal TBI ≤ 0.6 and severe PAD as TBI ≤ 0.2. In conclusion TBI can be reliably measured in patients with PAD and offer valuable information when diagnosing PAD. We present our diagnostic criteria based on clinical data.