The relevance of detecting carotid artery calcification on plain radiograph

The aim of this study was to determine the potential value of carotid artery calcification observed on plain radiographs in patients referred for carotid angiogram in the diagnosis of carotid artery stenosis.

One hundred sixty consecutive patients with suspected carotid artery stenosis underwent both plain radiographs of the carotid arteries and digital subtraction angiography of the same vessels. In addition, 108 of these patients also had duplex ultrasound of the same vascular area. The clinical usefulness of the carotid artery calcification was assessed by calculating the likelihood ratios for different test results against results of angiography and duplex ultrasound.

There is a statistically significant association between the degrees of calcification and carotid disease as demonstrated by angiography (P = .0001), although positive correlations of the degrees of stenosis and calcification was only fair (Spearman correlation coefficient r = .4). The sensitivity of carotid calcification in detecting clinically significant stenosis assuming any calcification is abnormal was 89% with a specificity of 46%. The likelihood ratios for 50% stenosis by angiography varied from 0.24 (no calcification) to 3.41 (level III) and for 50% stenosis by duplex ultrasound varied from 0.21 (no calcification) to more than 5.87 (level III). Assessments of the degree of calcification based on plain radiographs had excellent reproducibility (all intraclass correlation coefficients were greater than .9).

In this population with a high prevalence of carotid artery disease, there is an association between the presence of carotid calcification and atheromatous disease. If subsequent studies were to show this to apply in the general population, this could be of value in identifying asymptomatic patients at increased risk.