External Validation and Modification of Nationwide Inpatient Sample Subarachnoid Hemorrhage Severity Score

Sapna Rawal; Gabriel J E Rinkel; Jiming Fang; Chad W Washington; R Loch Macdonald; J Charles Victor; Timo Krings; Moira K Kapral; Andreas Laupacis

doi:10.1093/neuros/nyab237

External Validation and Modification of Nationwide Inpatient Sample Subarachnoid Hemorrhage Severity Score

Neurosurgery. 2021 Sep 15;89(4):591-596. doi: 10.1093/neuros/nyab237.

Authors

Sapna Rawal^{1

2}, Gabriel J E Rinkel³, Jiming Fang⁴, Chad W Washington⁵, R Loch Macdonald^{6

7}, J Charles Victor^{2

4}, Timo Krings¹, Moira K Kapral^{2

4

8

9}, Andreas Laupacis^{2

4

7}

Affiliations

¹ Division of Neuroradiology, Joint Department of Medical Imaging, Toronto Western Hospital, University Health Network, Toronto, Canada.
² Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada.
³ Department of Neurology and Neurosurgery, Brain Center Rudolf Magnus, University Medical Center, Utrecht, the Netherlands.
⁴ ICES, Toronto, Canada.
⁵ Department of Neurosurgery, University of Mississippi Medical Center, Jackson, Mississippi.
⁶ Division of Neurosurgery, Department of Surgery, St. Michael's Hospital, Labatt Family Centre of Excellence in Brain Injury and Trauma Research, Keenan Research Centre for Biomedical Research, University of Toronto, Toronto, Canada.
⁷ Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, Canada.
⁸ Division of General Internal Medicine and Toronto General Research Institute, University Health Network, Toronto, Canada.
⁹ Division of General Internal Medicine, Department of Medicine, University of Toronto, Toronto, Canada.

PMID: 34271587
DOI: 10.1093/neuros/nyab237

Abstract

Background: The Nationwide Inpatient Sample Subarachnoid Hemorrhage (SAH) Severity Score (NIS-SSS) was developed as a measure of SAH severity for use in administrative databases. The NIS-SSS consists of International Classification of Diseases Ninth Revision (ICD-9) diagnostic and procedure codes derived from the SAH inpatient course and has been validated against the Hunt-Hess score (HH).

Objective: To externally validate both the NIS-SSS and a modified version of the NIS-SSS (m-NIS-SSS) consisting of codes present only on admission, against the HH in a Canadian province-wide registry and administrative database of SAH patients.

Methods: A total of 1467 SAH patients admitted to Ontario stroke centers between 2003 and 2013 with recorded HH were included. The NIS-SSS and m-NIS-SSS were validated against the HH by testing correlation between the NIS-SSS/m-NIS-SSS and HH, comparing discriminative ability of the NIS-SSS/m-NIS-SSS vs HH for poor outcome by calculating area under the curve (AUC), and comparing calibration of the NIS-SSS, m-NIS-SSS, and HH by plotting predicted vs observed outcome.

Results: Correlation with HH was 0.417 (P ≤ .001) for NIS-SSS, and 0.403 (P ≤ .001) for m-NIS-SSS. AUC for prediction of poor outcome was 0.786 (0.764-0.808) for HH, 0.771 (0.748-0.793) for NIS-SSS, and 0.744 (0.721-0.767) for m-NIS-SSS. Calibration plots demonstrated that HH had the most accurate prediction of outcome, whereas the NIS-SSS and m-NIS-SSS did not accurately predict low risk of poor outcome.

Conclusion: The NIS-SSS and m-NIS-SSS have good external validity, and therefore, may be suitable to approximate traditional clinical scores of disease severity in SAH research using administrative data.

Keywords: Epidemiologic methods; Health services research; Subarachnoid hemorrhage.

Publication types

Research Support, Non-U.S. Gov't

MeSH terms

Canada
Hospitalization
Humans
Inpatients
Subarachnoid Hemorrhage* / diagnosis
Subarachnoid Hemorrhage* / epidemiology
Treatment Outcome