Ankle-Brachial Index (ABI) and Toe-Brachial Index (TBI) in Type 2 Diabetes Mellitus Patients with Peripheral Artery Disease (PAD) and Their Correlation with Carotid Intima Media Thickness (CIMT)

Background: Recent studies have shown that ankle brachial index (ABI) can be falsely normal even in presence of peripheral artery disease (PAD) of lower limbs in diabetes mellitus (DM) patients, especially in elderly and those with chronic kidney disease. In such patients, toe brachial index (TBI) seems to be a better screening test for detecting PAD. Objective: To compare the sensitivity between ABI and TBI for detecting PAD in type 2 DM patients; and to study the correlation between glycaemic control and severity of PAD. Methods: A cross-sectional study was performed in 75 type 2 DM patients with PAD of bilateral lower limbs, which was confirmed by CT angiography of lower limbs (a total 150 limbs were evaluated). They underwent Doppler for measurement of ABI and TBI. CIMT was measured using high-resolution B-mode ultrasonography. Results: There were 57 males and 18 females, with mean age of 65.72 years and mean duration of T2DM of 15.39 years. With a cut-off of 0.9, ABI had sensitivity of 68.66% and with cut-off of 0.7, TBI had sensitivity of 97.33% for detecting PAD, respectively. Age, smoking, hypertension and HbA1c correlated positively with severity of both ABI and TBI whereas serum creatinine correlated with only ABI severity. Age, hypertension, poor glycaemic control and serum creatinine positively correlated with severity of CIMT. Severity of CIMT, in turn, had a significant correlation with severity of both ABI and TBI. In a subgroup analysis, increasing age, longer duration of DM, higher waist circumference, higher serum creatinine and high LDL-C levels were associated with ABI >0.9; whereas poor glycaemic control (higher HbA1c and FBS) and smoking were associated with ABI <0.9; and gender and hypertension were not significantly different in groups with either ABI <0.9 or >0.9. ABI >0.9 was associated with slightly increased CIMT compared with ABI <0.9. Conclusion: In T2DM patients, TBI is more sensitive than ABI for detecting PAD, especially in elderly, those with longer duration of DM and impaired renal function.