Comparing Early National Institutes of Health Stroke Scale Versus 90-Day Modified Rankin Scale Outcomes in Acute Ischemic Stroke Trials: A Systematic Review and Analysis.

BACKGROUND

Early National Institutes of Health Stroke Scale (NIHSS) assessment may provide practical benefits over 90-day modified Rankin Scale (mRS), but it is unclear how it compares in adjudicating randomized clinical trial (RCT) results in acute ischemic stroke.

METHODS AND RESULTS

We searched Ovid Medline (inception to April 1, 2023) and included RCTs of acute therapies for acute ischemic stroke with data for both 90-day mRS and NIHSS within 7 days. Primary outcome was agreement between trial results (classified as positive, negative, or neutral) based on 24-hour NIHSS and 90-day mRS scores. We additionally assessed agreement for 2-hour, 48-hour, 72- to 96-hour, and 5- to 7-day NIHSS scores. We aimed to validate our findings using individual patient data from the ESCAPE (Randomized Assessment of Rapid Endovascular Treatment of Ischemic Stroke) and ESCAPE-NA1 (Safety and Efficacy of Nerinetide [NA-1] in Subjects Undergoing Endovascular Thrombectomy for Stroke) RCTs. We included 116 trials (44 387 patients), contributing 165 NIHSS assessments. The 24-hour NIHSS scores resulted in the same classification as 90-day mRS scores in 61/73 (83.6%) trials (Cohen's kappa, 0.64 [95% CI: 0.45-0.83] and Gwet's agreement coefficient 1, 0.79 [95% CI: 0.67-0.90]). Agreement was not statistically different by timing of NIHSS assessments (range 75%-100%, =0.33). Individual patient data showed higher agreement for assessments between 48 hours and 7 days, varying by NIHSS dichotomization cutoffs (NIHSS score, 0-2; 2 hours, 56.6%; 24 hours, 66.6%; 48 hours, 71.8%; 5-7 days: 76.5%, <0.01; NIHSS score, 0-7; 2 hours, 72.8%; 24 hours, 80.5%; 48 hours, 83.1%; 5-7 days: 84.7%, <0.01).

CONCLUSIONS

The 24-hour NIHSS scores aligned with 90-day mRS scores in 84% of RCT results, indicating intermediate-to-good agreement. However, individual patient data showed that early NIHSS risks misclassifying around 1/4 patients. These data contribute to a better understanding of the nuances of early NIHSS score as an outcome in acute ischemic stroke RCTs.