Background and Purpose: The aim of this study was to determine the pot
ential value of carotid artery calcification observed on plain radiogr
aphs in patients referred for carotid angiogram in the diagnosis of ca
rotid artery stenosis. Methods: One hundred sixty consecutive patients
with suspected carotid artery stenosis underwent both plain radiograp
hs of the carotid arteries and digital subtraction angiography of the
same vessels. In addition, 108 of these patients also had duplex ultra
sound of the same vascular area. The clinical usefulness of the caroti
d artery calcification was assessed by calculating the likelihood rati
os for different test results against results of angiography and duple
x ultrasound. Results: There is a statistically significant associatio
n between the degrees of calcification and carotid disease as demonstr
ated by angiography (P=.0001), although positive correlation of the de
grees of stenosis and calcification was only fair (Spearman correlatio
n coefficient r=.4). The sensitivity of carotid calcification in detec
ting clinically significant stenosis assuming any calcification is abn
ormal 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 d
egree of calcification based on plain radiographs had excellent reprod
ucibility (all intraclass correlation coefficients were greater than .
9). Conclusions: In this population with a high prevalence of carotid
artery disease, there is an association between the presence of caroti
d calcification and atheromatous disease. If subsequent studies were t
o show this to apply in the general population, this could be of value
in identifying asymptomatic patients at increased risk.