Role of Ankle Brachial Index (ABI) in Prediction of Peripheral Arterial Disease among Asymptomatic Patients with Atherosclerotic Risk Factors

Peripheral Arterial Disease (PAD) is significantly associated with Cardio-Vascular and Cerebro-Vascular diseases. Since the risk of atherosclerosis increases with increasing age, the incidence and prevalence of PAD are rising with the aging world population. Hence, early diagnosis and appropriate treatment of PAD is considered essential to prevent mortality and morbidity associated with it. Numerous radiological or non-radiological tests are available to detect PAD in symptomatic patients. However, pre-clinical diagnosis is difficult due to the absence of symptoms. Therefore, the need for a simple, non-invasive method, which can detect PAD accurately in the early stages, is essential. Among the various available means, the Ankle Brachial Index (ABI) has shown promising results not only in screening but also in establishing the severity of PAD. However, the role of ABI in detecting PAD among asymptomatic patients with atherosclerotic risk factors, has rarely been studied. This was a prospective, observational study conducted at a tertiary care Armed Forces hospital in India. It included 310 subjects (620 limbs) of age more than 40 years, who had one or more atherosclerotic risk factors but were asymptomatic for PAD. Demographic profile, clinical data, ABI, and findings of arterial doppler were recorded, and the data so collected were analysed. The prevalence of PAD was found to be 10.3% (considering ABI < 0.9 as PAD). The increasing age was significantly associated with PAD with p-value of 0.03601. A significant association (p-value < 0.05) between number of risk factors and prevalence of PAD was also observed. ABI had a sensitivity (Sn) of 93.75%, a specificity (Sp) of 97.48%, a positive predictive value (PPV) of 81.08%, and a negative predictive value (NPV) of 99.27% in detection of PAD, when the results were compared with the arterial Doppler scan. ABI can be used as a cost-effective screening tool for detection of PAD in the sub-clinical stage among patients with atherosclerotic risk factors.