Validity of a Retrospective National Institutes of Health Stroke Scale Scoring Methodology in Patients With Severe Stroke

Abstract

Quantifying stroke severity is essential for interpreting outcomes in stroke studies; severity impacts outcomes. Because outcome studies often enroll patients some time after stroke and there is little standardization of the history and physical examination, objective measurement of stroke severity is limited. A method for retrospectively scoring the National Institutes of Health Stroke Scale (NIHSS) based on history and physical examination has been proposed, but has yet to be validated in patients with higher NIHSS score. We evaluate the validity of this scoring method across the spectrum of the NIHSS scores. The retrospective scoring algorithm was applied to history and physical examinations documented for 58 patients with ischemic stroke presenting to any of 17 regional acute care facilities who had a NIHSS score recorded by a stroke team physician. The retrospective NIHSS score was obtained by standardized chart review. Linear regression was used to estimate scale-dependent and scale-independent bias. Limits of agreement quantify deviation of the retrospective NIHSS score from the prospective NIHSS score. Mean (SD) age at stroke was 66 (14) years; 27 (46.6%) patients were men, and 38 (65.5%) were white. The mean (SD) prospective NIHSS score was 13.6 (7.8); the mean (SD) retrospective NIHSS score was 13.7 (7.8). There were 23 (40%) prospective NIHSS scores above 15, and 13 scores (22%) above 20. The linear regression constant was 0.290 (95% confidence interval -0.107, 0.687); the slope was 0.987 (95% confidence interval 0.962, 1.013). The R(2) for the model was 0.991. Limits of agreement were -1.35 and 1.59. The retrospective NIHSS appears valid across the entire spectrum of scores.