Modified National Institutes of Health Stroke Scale for use in stroke clinical trials: prospective reliability and validity

Abstract

Background and purpose: To prospectively evaluate the reliability and validity of this previously developed stroke scale in an independently collected cohort. The National Institutes of Health Stroke Scale (NIHSS) has been criticized for its complexity and variability. Prior formal clinimetric analyses were used to obtain a modified version of NIHSS (mNIHSS), which retrospectively demonstrated improved reliability and validity. We sought to prospectively measure the reliability and validity of the mNIHSS.

Methods: Forty-five patients with a history of stroke or intracerebral hemorrhage were evaluated at the University of California, San Diego, Stroke Center from September 2000 through March 2001. Each patient was tested by 2 NIHSS-certified neurologists using the NIHSS, mNIHSS, Barthel Index, and Modified Rankin scales.

Results: There were a large percentage of high kappa values using the mNIHSS. Only 10 (66.67%) of 15 NIHSS kappa scores showed excellent agreement, whereas 10 (90.91%) of 11 mNIHSS kappa scores showed excellent agreement. As predicted, the mNIHSS was more reliable than the NIHSS because of the exclusion of items with low kappa values. With the use of correlation coefficient analysis, the mNIHSS was as valid as the NIHSS.

Conclusions: This prospective study found high reliability and continued validity by using a previously developed mNIHSS. Items found to have low kappa values were consistent with the previously derived retrospective mNIHSS. The resulting mNIHSS scale has much higher kappa values. The mNIHSS showed improved agreement between examiners and was also easier to administer, having fewer and simpler items. Further prospective evaluation should assess whether the mNIHSS could be used in lieu of the NIHSS.