Comparison of colour duplex ultrasound and ankle-brachial pressure index measurements in peripheral vascular disease in type 2 diabetic patients with foot infections

Abstract

Background and Objectives: Peripheral vascular disease (PVD) is a common cause of morbidity and mortality and is reported to be more common among diabetic subjects compared to non-diabetic subjects. The aim of the study was to compare the specificity and sensitivity of ankle-brachial index (ABI) measured by peripheral doppler with the colour duplex ultrasound (CDU) for diagnosis of PVD. Methods: One hundred type 2 diabetic patients admitted to our diabetic centre with foot lesions underwent both colour duplex ultrasound and ankle-brachial index measurements. PVD was diagnosed if the individual had haemodynamically significant obstruction on CDU, or if the ABI was < 0.9. The sensitivity and specificity of ABI was determined using the CDU as `gold standard'. Results: The mean age of the study group was 59.5 ± 10.1 years and the mean duration of diabetes was 11.7 ± 8.1 years. Of the total 100 subjects, six subjects had calcification of peripheral vessels and they were not included while calculating for sensitivity and specificity of ABI. Twenty (21.3%) subjects diagnosed as PVD by the CDU were not classified as PVD by the ABI measurements. Conversely, only three subjects (3.2%) classified as PVD by ABI had normal arteries based on CDU scanning. Overall, ABI had low sensitivity (70.6%) but a high specificity (88.5%). The overall agreement between CDU and ABI was poor (k=0.20). Conclusion: ABI is a good initial screening tool but some patients with significant stenosis in lower extremities would be missed, if ABI measurement alone is used for diagnosis of PVD.