Validation and modification of the Ottawa subarachnoid haemorrhage rule in risk stratification of Asian Chinese patients with acute headache.

OBJECTIVE: To validate the Ottawa subarachnoid haemorrhage (SAH) rule in an Asian Chinese cohort and to explore the roles of blood pressure and vomiting in prediction of SAH in patients with nontraumatic acute headache.
METHODS: A retrospective cohort study was conducted in two regional hospitals. All patients aged ≥16 years who presented with non-traumatic acute headache to the study centres from July 2013 to June 2016 were included. A logistic regression model was created for the variables of the Ottawa SAH rule and other potential predictors, including vomiting and systolic blood pressure (SBP) >160 mm Hg. Model discrimination was evaluated using the area under the receiver operating characteristic curve. Net reclassification improvement and integrated discrimination improvement indices were evaluated. The model's diagnostic characteristics, including sensitivities and specificities, were evaluated.
RESULTS: A total of 500 eligible headache cases were included, in 50 of which SAH was confirmed (10%). In addition to the predictors of the Ottawa SAH rule, vomiting and SBP >160 mm Hg were found to be significant independent predictors of SAH. Net reclassification improvement and integrated discrimination improvement indices indicated that including vomiting and SBP >160 mm Hg would improve the model prediction. The Ottawa SAH rule had 94% sensitivity and 32.9% specificity. The modified Ottawa SAH rule that included both vomiting and SBP >160 mm Hg as criteria improved sensitivity to 100%, specificity to 13.1%, positive predictive value to 11.3%, and negative predictive value to 100%.
CONCLUSIONS: The Ottawa SAH rule demonstrated high sensitivity. Addition of vomiting and SBP >160 mm Hg to the Ottawa SAH rule may increase its sensitivity.