Observer variability of an angiographic grading scale used for the assessment of intracranial aneurysms treated with flow-diverting stents

BACKGROUND AND PURPOSE: Novel angiographic grading scales for the assessment of intracranial aneurysms treated with flowdiverting stents have been recently developed because previous angiographic grading scales cannot be applied to these aneurysms. The purpose of this study was to evaluate the inter- and intraobserver variability of the novel O'Kelly Marotta grading scale, which was developed specifically for the angiographic assessment of aneurysms treated with flow-diverting stents. MATERIALS AND METHODS: Multiple raters (n = 31) from the disciplines of neuroradiology and neurosurgery were presented with preand posttreatment angiographic images of 14 aneurysms treated with intraluminal flow diverters. Raters were asked to classify pre- and posttreatment angiograms by using the OKM grading scale. Statistical analyses were subsequently performed with calculation of a generalized multirater k statistic for assessment of inter- and intraobserver variability and by performing a Wilcoxon signed rank sum test for assessment of group differences. RESULTS: Variability analysis of theOKMgrading scale yielded substantial (k=0.74) and almost perfect (k=0.99) inter- and intraobserver agreement, respectively, with no statistically significant differences between raters with a background of neuroradiology versus neurosurgery or attending physician versus trainee. CONCLUSIONS: The OKM grading scale for the assessment of intracranial aneurysms treated with flow-diverting stents is a reliable grading scale that can be used equally well by users of varying backgrounds and levels of training. Comparison with interobserver variability of pre-existing angiographic grading scales shows equal or better performance.