Inter-observer variability in the angiographic assessment of renal artery stenosis

Objective To assess inter-observer agreement in the interpretation of renal angiograms. Design Comparison of the assessment of renal angiograms by three experience d radiologists, who evaluated the number of renal arteries and the presence , location, aspect and severity of a renal artery stenosis. Setting General hospital and university hospital serving urban and rural po pulations. Patients Patients with difficult-to-treat hypertension referred for diagnos tic work-up; 312 angiograms with the intra-arterial digital subtraction tec hnique were obtained from 289 consecutive patients. Main outcome measures Inter-observer agreement was tested for the following parameters: number of arteries per kidney, presence of stenosis, location of stenosis (truncal, ostial), aspect of stenosis (concentric, eccentric, p oststenotic dilatation), severity of stenosis (reduction of lumen diameter in categories of 30%, 40%, etc, to 100%), and overall quality of the angiog raphic images. Kappa (kappa) values and weighted kappa between the three pa irs of radiologists were used as estimates of inter-observer agreement. Results Agreement about the number of renal arteries was reasonable (kappa = 0.50-0.72), as was agreement about the presence of stenosis (kappa = 0.68 -0.86). Agreement: about stenosis location and aspect was poor (kappa = 0.2 6-0.47 and kappa = 0.15-0.26, respectively), There was general agreement ab out the severity of stenosis (weighted kappa = 0.65-0.70), but it was not p ossible to distinguish between 50 and 60% stenosis or between 60 and 70% st enosis (kappa < 0.40). No correlation was found between agreement on severi ty of stenosis and the quality of the images. Conclusions It is not realistic to make statements about what degree of ren al artery stenosis is clinically significant, as long as the intra-arterial angiogram with digital subtraction remains the gold standard. It is likewi se risky to rely too strongly on stenosis morphology as visualized by renal angiography in choosing between balloon angioplasty and stent deployment. J Hypertens 1999, 17:1731-1736 (C) Lippincott Williams & Wilkins.