Capillary Index Score in acute ischemic stroke: interobserver reliability and correlation with neurological outcomes

Collateral blood flow has been identified as a possible factor to evaluate when predicting neurological outcomes or selecting patients for endovascular therapy in acute ischemic stroke. The Capillary Index Score (CIS) has recently been proposed as a tool to select patients with sufficient collateral blood flow for vascularization and to predict good neurological outcomes. We investigated the inter-rater agreement among reviewers of CIS and compared consensus scores to neurological outcomes.

We conducted a retrospective review of 29 randomly selected patients undergoing endovascular therapy for an occlusion in the middle cerebral artery or intracranial internal carotid artery. Patients' angiograms were reviewed by four reviewers of varying experience levels and given a CIS ranging from 0-3. A favorable CIS was 2 or 3 and an unfavorable CIS was 0 or 1. The inter-agreement of the reviewers was calculated using the κ statistic. A consensus CIS was compared with good neurological outcome, defined as modified Rankin Scale scores (mRS≤2) at 90 days.

The agreement between reviewers for the CIS ranged from κ=0.66-0.97, indicating good to very good agreement. 92% of patients with favorable CIS had a positive neurological outcome compared to only 14% of unfavorable CIS patients. The number of patients with a favorable neurological outcome (mRS≤2) at 90 days was higher in the favorable CIS group (P<0.0001).

CIS was a reproducible metric among physicians of varying experiences. Favorable CIS scores were a predictor of good neurological outcome and lower rates of intracranial hemorrhage. We believe that the Capillary Index Score can be used alongside other tools to improve patient selection for endovascular treatment.