The National Institutes of Health Stroke Scale (NIHSS) and Scandinavian Stroke Scale (SSS) are both validated measures of neurologic impairment and have been used in many acute stroke trials. Methods for interconverting SSS and NIHSS are needed.
Conversion equations were developed using linear regression (both unadjusted, and adjusted for age and sex) using a random 50% of the data at both baseline and 90 days. The remaining 50% of data were used to test the accuracy of the models produced.
Data from 5 acute stroke trials (2004 patients) were included. Fitted models at baseline were NIHSS = 25.68 – 0.43 ∗ SSS (R2 = 0.57, prediction error [PE] –0.2, P = .20), and SSS = 50.37 – 1.63 ∗ NIHSS (R2 = 0.59, PE 0.2, P = .35). The 90-day models were NIHSS = 22.99 – 0.39 ∗ SSS (R2 = 0.82, PE –0.3, P = .001), and SSS = 56.68 – 2.20 ∗ NIHSS (R2 = 0.80, PE –0.4, P = .08). Adjustment did not materially improve the R2 values.
Total scores for NIHSS and SSS may be interconverted with good precision; the mathematic conversion equations may prove useful in clinical practice and in comparison of data from observational studies and randomized trials.
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Accepted: February 11, 2009
Received in revised form: January 29, 2009
Received: January 5, 2009
Dr. Gray is supported, in part, by The Stroke Association (UK) and Medical Research Council (UK). Prof. Bath is Stroke Association Professor of Stroke Medicine.
Presented as a poster at the European Stroke Conference in Glasgow in May 2008.
© 2009 National Stroke Association. Published by Elsevier Inc. All rights reserved.