The Reliability and Sensitivity of the National Institutes of Health Stroke Scale for Spontaneous Intracerebral Hemorrhage in an Uncontrolled Setting

Background and Purpose: The National Institutes of Health Stroke Scale (NIHSS) is commonly used to measure neurologic function and guide treatment after spontaneous intracerebral hemorrhage (ICH) in routine stroke clinics. We evaluated its reliability and sensitivity to detect change with consecutive and unique rater combinations in a real-world setting. Methods: Conservative measures of interrater reliability (unweighted Kappa (kappa), Intraclass Correlation Coefficient (ICC1.1) and sensitivity to detect change (Minimal Detectable Difference (MDD)) were estimated. Sixty-one repeated ratings were completed within 1 week after ICH by physicians and nurses with no investigator intervention. Results: Reliability (consistency) of the NIHSS total score was good for both physicians vs. nurses and nurses vs. nurses (ICC=0.78, 95%CI: 0.58-0.89 and ICC= 0.75, 95% CI: 0.55-0.87 respectively) in this scenario. Reliability (agreement) of items 1C and 9 were excellent (kappa>=0.61) for both rater comparisons, however, reliability was poor to fair on most remaining items (kappa:0.01-0.60), with item 11 being completely unreliable in this scenario (kappa<0.01). The MDD95 of the total NIHSS score was +/- 10 and +/- 11 points for physician vs. nurse and nurse vs. nurse comparisons. Conclusions: The reliability of the NIHSS is good overall for ICH even in an uncontrolled setting. However, on repeated measurements changes in total NIHSS score of at least >=10 points need to be observed for clinicians to be confident that real changes had occurred within 1 week after ICH.