Colour duplex ultrasonography versus angiography in the diagnosis of lower-extremity arterial disease

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Abstract
Colour duplex scanning is reported to be an accurate non-invasive tool for the diagnosis of lower-extremity arterial disease. The authors at the South Coast Vascular Laboratory have conducted a prospective audit to determine the efficacy of colour duplex scanning in a vascular surgical practice. The aims of this prospective trial were to compare the accuracy of colour duplex scanning with intra-arterial digital subtraction angiography (DSA) in the localization and classification of aortoiliac and femoropopliteal artery disease. Ninety-one lower limbs in 50 patients were evaluated independently by colour duplex scanning and DSA. The lower-limb vasculature was divided into eight segments: infrarenal aorta, common iliac artery, external iliac artery, common femoral artery, proximal, middle and lower thirds of the combined length of the superficial femoral and above-knee popliteal artery, and lastly the below-knee popliteal artery. A total of 558 arterial segments were examined. The Kappa value of duplex scanning compared with ‘gold standard’ DSA was 0.57. For detecting haemodynamically significant arterial lesions of >50% reduction in diameter, duplex scanning had a sensitivity of 75%, specificity of 90%, positive predictive value of 77% and negative predictive value of 89% compared with DSA. The level of accuracy obtained does not support the use of duplex as a sole method of investigation for lower-extremity arterial disease in the authors' case. However, the high negative predictive value of colour duplex may be useful in excluding haemodynamically significant disease. This study emphasizes the importance of prospective auditing to determine individual accuracy with duplex examination for arterial disease, and enables clinical decision making to be based on tests with a known accuracy.