Addition of sodium criterion to SOAR stroke score

Objectives: To examine the usefulness of including sodium (Na) levels as a criterion to the SOAR stroke score in predicting inpatient and 7-day mortality in stroke. 
Materials & Methods: Data from the Norfolk and Norwich University Hospital Stroke & TIA register (2003-2015) were analysed. Univariate and then multivariate models controlling for SOAR variables were used to assess the association between admission sodium levels and inpatient and 7-day mortality. The prognostic ability of the SOAR and SOAR-Na score for mortality outcomes at both time points were then compared using Area Under the Curve (AUC) values from Receiver Operating Characteristics. 
Results: A total of 8,493 cases were included (male=47.4%, mean (s. d.) 77.7 (11.6) years). Compared to normonatraemia (135-145mmol/L), hypernatraemia (>145mmol/L) was associated with inpatient mortality and moderate (125-129mmol/L) and severe hypontraemia (<125mmol/L) with 7-day mortality after adjustment for stroke type, Oxfordshire Community Stroke Project classification, age, pre-stroke modified Rankin score and sex. The SOAR and SOAR-Na scores both performed well in predicting inpatient mortality with AUC values of 0.794(0.78-0.81) and 0.796(0.78-0.81), respectively. 7-day mortality showed similar results. Both scores were less predictive in those with chronic kidney disease (CKD) and more so in those with hypoglycaemia. 
Conclusion: The SOAR-Na did not perform considerably better than the SOAR stroke score. However, the performance of SOAR-Na in those with CKD and dysglycaemias requires further investigation.