Distributional Validity and Prognostic Power of the National Institutes of Health Stroke Scale in US Administrative Claims Data

Importance: Comparative assessment of acute ischemic stroke care quality provided by hospitals in the United States has been hampered by the unavailability of the National Institutes of Health Stroke Scale (NIHSS) in administrative data sets, preventing adequate adjustment for variations in patient case-mix risk. In response to stakeholder concerns, the US Centers for Medicare median interquartile range age, 72 61-82 years). Median (interquartile range) NIHSS score was 4 (2-11), and frequency of severity categories included absent (NIHSS score, 0) in 2080 patients (9.6%), minor (NIHSS score, 1-4) in 8760 patients (40.4%), and severe (NIHSS score, 21-42) in 1930 patients (8.9%). National Institutes of Health Stroke Scale score of 10 or more, an indicator of possible large vessel occlusions, was present in 6290 patients (29%). Presenting NIHSS score was higher in very elderly patients (age ≥80 y) and women and also in patients receiving endovascular thrombectomy vs intravenous thrombolysis alone vs no reperfusion therapy (median interquartile range, 17 12-22 vs 6 4-12 vs 4 2-9, respectively) (P < .001). National Institutes of Health Stroke Scale scores were similarly higher for discharge outcomes of mortality vs discharge to skilled nursing facility vs discharge home (median interquartile range, 19 12-25 vs 7 3-15 vs 2 1-5, respectively) (P < .001). Likelihood of NIHSS scores being reported independently increased with interfacility transfer, receipt of acute reperfusion therapies, larger hospital size, academic centers, and region other than the West. Conclusions and Relevance: In the initial national optional reporting period in the United States, NIHSS scores were reported in nearly 1 in 7 ischemic stroke hospitalizations. The distribution of NIHSS scores was similar to that from narrow population-based studies and registries, and NIHSS scores were powerfully associated with discharge outcome, supporting the validity and potential to aid care quality assessment.