Effect of calcified plaques on estimation of arterial stenosis of lower extremity in diabetic foot patients using multislice computed tomography angiography

Objective To investigate the impacts of calcified plaques on estimation of arterial stenosis of lower extremity in diabetic foot patients using 16-slice computed tomography angiography(MSCTA). Materials and Methods Thirty-five patients(representing 38 cases)underwent both MSCTA and digital subtraction angiography(DSA) examinations. The arteries of lower extremity were divided into 15 anatomic segments, and the degree of artery stenosis in each segment was classified as normal, mildly, moderately, severely or occluded. The extent of calcification in each segment was also assessed on cross-sectional image of MDCTA and was classified as absent, mildly,moderately, or severely. Using DSA as the standard reference, the sensitivity, specificity, accuracy, Youden index,positive predictive value and negative predictive value of MSCTA were calculated. Agreement between MSCTA and DSA was assessed by Cohen's kappa statistics. Results In the noncalcified, mildly and moderately calcified segments of the artery above the knee, for the detection of segments that had more than mild stenosis, the sensitivity,specificity, accuracy, Youden index, positive predictive value and negative predictive value of MSCTA were 97.1%,98.7%, 98.2%, 95.8%, 97.0% and 98.7%, respectively. In the severely calcified segments of the artery above the knee, for the detection of segments that had more than mild stenosis, the sensitivity, specificity, accuracy, Youden index, positive predictive value and negative predictive value of MSCTA were 96.3%, 93.8%, 94.7%, 90.1%,89.7% and 97.8%, respectively. In the noncalcified, mildly and moderately calcified segments of the artery below the knee, for the detection of segments that had more than mild stenosis, the sensitivity, specificity, accuracy, Youden index, positive predictive value and negative predictive value of MSCTA were 95.1%, 93.2%, 94.1%, 88.3%,93.4% and 94.9%, respectively. In the severely calcified segments of the artery below the knee, for the detection of segments that had more than mild stenosis, the sensitivity, specificity, accuracy, Youden index, positive predictive value and negative predictive value of MSCTA were 100%, 73.9%, 89.3%, 73.9%, 84.6% and 100%, respectively.Good diagnostic agreement between MSCTA and DSA was achieved for the noncalcified, mildly and moderately calcified artery segments above the knee(κ =0.958, P 0.01), for severely calcified artery segments above the knee(κ =0.887,P 0.01), and for noncalcified, mildly and moderately calcified artery segments below the knee( κ =0.882,P 0.01). In the severely calcified artery segments below the knee κ value showed a moderate agreement(κ =0.770,P 0.01). Conclusion When the stenosis degree of lower extremity arteries in diabetic foot patients were evaluated with MSCTA, all evaluating indicators of severely calcified arteries are mildly lower than those not severely calcified arteries above the knee, and the specificity and positive predictive value of severely calcified arteries are significantly lower than those of not severely calcified arteries below the knee, and the specificity and negative predictive value are higher than those not severely calcified arteries below the knee. Stenosis degree may be overestimated in severe calcification arteries below the knee with MSCTA.