Gr. Young et al., OBSERVER VARIATION IN THE INTERPRETATION OF INTRAARTERIAL ANGIOGRAMS AND THE RISK OF INAPPROPRIATE DECISIONS ABOUT CAROTID ENDARTERECTOMY, Journal of Neurology, Neurosurgery and Psychiatry, 60(2), 1996, pp. 152-157
Objective-To determine how often observer variation in the interpretat
ion of intra-arterial angiograms might alter the decision whether or n
ot to refer patients for carotid surgery. Methods-A prospective study
was carried out in a consecutive series of 99 patients with transient
ischaemic attacks and minor strokes. Interpretable angiographic films
were available for 179 carotid artery bifurcations. Stenosis of the in
ternal carotid artery was measured using mm scales, independently by t
hree different radiologists (A, B, and C), using the European Carotid
Surgery Trial method. Results-An analysis of the grouped data showed g
ood to moderate agreement by kappa statistics for radiologists A upsil
on B, B upsilon C, and A upsilon C of 0.68, 0.60, and 0.70 respectivel
y. The mean absolute difference in the estimate of stenosis by each of
the different radiologists (interobserver variation) was 9.5% and for
each radiologist on two separate occasions (intraobserver variation)
8.4%. The degree of observer error was smallest among severely stenose
d arteries. Although the absolute differences were small, ((clinically
important'' diferences which could change the treatment recommended f
rom surgery to no surgery (or vice versa) occurred between radiologist
s A and B, B and C, and A and C in: seven (3.9%), six (3.4%), and 11 (
6.1%) vessels respectively. Conclusions-Because observer variation aff
ects all of the imaging methods (Doppler, duplex, contrast arteriograp
hy, and MR angiography) used to select patients with transient ischaem
ic attack and stroke, these findings are Likely to be widely relevant.
Any centre assessing patients with cerebrovascular disease will need
to implement strict quality control measures in the interpretation of
angiograms (and other vascular imaging procedures) to minimise observe
r error and thereby reduce the number of inappropriate decisions made
to refer for carotid artery surgery or not.