Observer Variability of an Angiographic Grading Scale Used for the Assessment of Intracranial Aneurysms Treated with Flow-Diverting Stents

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Fig 1.
OKM angiographic grading scale for assessment of aneurysms treated with flow-diverting stents. Aneurysms are assigned grades on the basis of the amount of contrast filling of the aneurysm lumen (filling grades, A, B, C, D) and how long contrast persists in the aneurysm lumen with respect to angiographic phase (stasis grades 1, 2, 3). A grade consisting of a letter and a number is assigned to an aneurysm (eg, an aneurysm that fills its lumen completely with contrast persisting within the lumen into the venous phase of the angiogram is assigned grade A3).² Modified from O'Kelly CJ, Krings T, Fiorella D, et al. A novel grading scale for the angiographic assessment of intracranial aneurysms treated using flow diverting stents. Interv Neuroradiol 2010;16:133–37 and reproduced with permission from Centauro srl Publishing.

Table 1:

Individual and group variability for the OKM grading scale

Variability		Statistical Value
Individual
Interobserver	Substantial agreement	κ = 0.74 (P < .005)^{^a}
Intraobserver	Almost perfect agreement	κ = 0.99 (P < .005)^{^a}
Group
Neuroradiology vs neurosurgery	No significant difference in interpretation	P = .329^{^b}
Trainee vs attending	No significant difference in interpretation	P = .2^{^b}

Table 3:

Comparison of interobserver variability (κ) of the OKM grading scale and other angiographic grading scales

Scale	Parameters	κ	Reference
Aneurysms	12 Possibilities	0.74	This article
Flow-diversion stents	Filling grade: A, B, C, D
OKM scale	Stasis grades: 1, 2, 3
Aneurysms	4 Possibilities	0.50	Cloft et al, 2007⁸
Coiled	Complete, dog-ear, residual neck, residual aneurysm
4-Point Raymond scale
Aneurysms	3 possibilities	0.54	Cloft et al, 2007⁸
Coiled	Complete, near-complete, incomplete
3-Point scale
AVMs	7 Possibilities	0.47	Al-Shahi et al, 2002⁹
Spetzler-Martin scale	Nidus size: 1, 2, 3;
	eloquence: 0, 1;	0.70	Iancu-Gontard et al, 2007¹⁰
	venous drainage: 0, 1