Retrospective NIH Stroke Scale: Not Applicable Without Initial Evaluation by a Neurologist
Background and Purpose: The NIH Stroke Scale (NIHSS) and the Canadian Neurological Scale (CNS) have been reported to be useful for the retrospective assessment of initial stroke severity. However, the NIHSS requires detailed neurological assessments that may not be reflected in all patient records, potentially limiting its applicability. We assessed the reliability of the retrospective algorithms and the proportions of missing items for the NIHSS and CNS in stroke patients admitted to an academic medical center and 2 community hospitals. Methods: Randomly selected records of patients with ischemic stroke admitted to an academic medical center (AMC, n=20), and community hospitals with (CH1, n=19) and without (CH2, n=20) acute neurological consultative services were reviewed. NIHSS and CNS scores were assigned independently by two neurologists using published algorithms. Inter-rater reliability of the scores was determined with the intraclass correlation coefficient (ICC), and numbers of missing items were tabulated. Results: The ICCs for NIHSS and CNS respectively were 0.93 (95% CI 0.82–1.0) and 0.97 (0.90–1.0) for the AMC, 0.89 (0.75–1.0) and 0.88 (0.73–1.0) for CH1, and 0.48 (0.26–0.70) and 0.78 (0.6–0.96) for CH2. More NIHSS items were missing at CH2 (62%) vs. the AMC (27%) and CH1 (23%, p=0.0001). In comparison, 33%, 0%, and 8%, of CNS items were missing from records from CH2, AMC, and CH1, respectively (p=0.0001). The ICCs for NIHSS missing items were 0.53 (95% CI 0.31–0.75), 0.7 (0.5–0.9), 0.64 (0.42–0.85), for the 3 hospitals, respectively. Conclusions: There are substantial levels of agreement for retrospectively-assigned NIHSS and CNS scores for patients initially evaluated by a neurologist at both an AMC and a CH. However, the proportions of missing items are higher for the NIHSS in each setting, effectively reducing it to the items captured on the CNS, and particularly limiting the NIHSS application in hospitals without acute neurological consultative services.