Interobserver agreement and predictive value for outcome of two rating scales for the amount of extravasated blood after aneurysmal subarachnoid haemorrhage

Abstract

Background: In patients with SAH the amount of extravasated blood on the initial CT scan is related with delayed cerebral ischemia and clinical outcome. We investigated the interobserver variation of the Hijdra and Fisher scales for the amount of extravasated blood and the predictive values of these scales for delayed cerebral ischemia and outcome.

Methods: For 132 patients admitted within 48 hours after SAH three observers assessed the amount of blood on the initial CT scan by means of the Hijdra and Fisher scale. We analyzed interobserver agreement with kappa statistics and used multivariate logistic regression for the association with delayed cerebral ischemia and clinical outcome.

Results: The interobserver agreement of all three pairs of observers was good for the Hijdra scale (kappas for total sum scores ranging from 0.67 to 0.75) and mild to moderate for the Fisher scale (kappas ranging from 0.37 to 0.55). For the Hijdra scale the risk of DCI was higher for intermediate (OR 4.2; 95% CI 1.1-16.3) and large (OR 3.6; 95% CI 0.8-16.4) amounts of blood with small amount as reference. Fisher grade III (OR 1.0; 95% CI 0.2-5.2) and IV (OR 0.3; 95% CI 0.02-4.0) were not related with DCI. For the Hijdra scale and clinical outcome we found an increasing risk for poor outcome with intermediate (OR 3.9; 95% CI 1.0-15.9) and large (OR 10.7; 95% CI 2.3-50.1) amounts of blood. Such a relation was not found for Fisher grade III (OR 1.2; 95% CI 0.2-7.0) and IV (OR 0.2; 95% CI 0.01-3.4).

Conclusions: For the Hijdra scale we found a distinct better interobserver agreement than for the Fisher score. Moreover, the Hijdra scale was an independent prognosticator for DCI and clinical outcome, which was not the case for the Fisher score.