Inter- and intraobserver agreement in scoring angiographic results of intra-arterial stroke therapy

Angiographic results are commonly used as surrogate markers of the success of intra-arterial therapies for acute stroke. Inter- and intraobserver agreement in judging angiographic results remain poorly characterized. Our goal was to assess 2 commonly used revascularization scales.

A portfolio of 148 pre- and post treatment images of 37 cases of proximal anterior circulation occlusions was electronically sent to 12 expert observers who were asked to grade treatment outcomes according to recanalization (of arterial occlusive lesion) or reperfusion (TICI) scales. Three expert observers had to score treatment outcomes by using a similar portfolio of 32 patients or when they had full access to all angiographic data, twice for each method 3-12 months apart. Results were analyzed by using κ statistics.

Agreement among 9 responding observers was moderate for both the TICI (κ = 0.45 ± 0.01) and arterial occlusive lesion (κ = 0.39 ± 0.16) scales. Agreement was similar (moderate) when 3 observers had access to a portfolio (κ = 0.59 ± 0.06 and 0.49 ± 0.07, respectively) or to the full angiographic data (κ = 0.54 ± 0.06 and 0.59 ± 0.07, respectively). Intraobserver agreement was "fair to moderate" for both methods. Interobserver agreement became "substantial" (>0.6) when outcomes were dichotomized into "success" (TICI 2b, 3; arterial occlusive lesion II, III or "failure"; the results were judged more favorably when the arterial occlusive lesion rather than the TICI scale was used.

There is an important variability in the assessment of angiographic outcomes of endovascular treatments, invalidating comparisons among publications. A simple dichotomous judgment can be used as a surrogate outcome when treatments are assessed by the same observers in randomized trials.