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.