Hospital volume and stroke outcome
Does it matter?
Abstract
Background: Although hospital–outcome relationships have been explored for a variety of procedures and interventions, little is known about the association between annual stroke admission volumes and stroke mortality. Our aim was to determine whether facility type and hospital volume was associated with stroke mortality.
Methods: All hospital admissions for ischemic stroke were identified from the Hospital Morbidity database (HMDB) from April 2003 to March 2004. The HMDB is a national database that contains patient-level sociodemographic, diagnostic, procedural, and administrative information across Canada. Ischemic stroke was identified through patient's principal diagnosis recorded using the International Classification of Diseases (9 and 10). Multivariable analysis was performed with generalized estimating equations with adjustment for demographic characteristics, provider specialty, facility type, hospital volume, and clustering of observations at institutions.
Results: Overall, 26,676 patients with ischemic stroke were admitted to 606 hospitals. Seven-day stroke mortality was 7.6% and mortality at discharge was 15.6%. Adverse outcomes were more frequent in patients treated in low-volume facilities (<50 strokes/year) than in those treated in high volume facilities (100 to 199 and >200 strokes patients/year) (for 7-day mortality: 9.5 vs 7.3%, p < 0.001; 9.5 vs 6.0%, p < 0.001; for discharge mortality: 18.2 vs 15.2%, p < 0.001; 18.2 vs 12.8%, p < 0.001). The difference persisted after multivariable adjustment or when hospital volume was divided into quartiles.
Conclusions: High annual hospital volume was consistently associated with lower stroke mortality. Our study encourages further research to determine whether this is due to differences in case mix, more organized care in high-volume facilities, or differences in the performance or in the processes of care among facilities.
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Published online: July 18, 2007
Published in print: September 11, 2007
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Saposnik et al provide strong evidence that hospital volume generally predicts in-hospital mortality. [1] This begs the question whether in-hospital mortality is the best—or even a good— measure of stroke outcome. Did volume influence functional outcome or mortality at 3, 6, and 12 months?
Reference
1. Saposnik G, Baibergenova A, O'Donnell M, Hill MD, Kapral MK, V. Hachinski On behalf of the Stroke Outcome Research Canada (SORCan) Working Group. Hospital volume and stroke outcome. Neurology 2007; 0: 01.wnl.0000268485.93349.58v1
Disclosure: The author reports no conflicts of interest.
We appreciate Dr. Gordon's interest and comments regarding our recently published article. [1] Unfortunately, we have no information about functional or long-term outcomes. We are currently working to further analyze the impact of organized care on stroke outcomes at 7 days, 30 days and 1 year.
Disclosure: Dr. Gustavo Saposnik received supprt from Heart Stroke Foundation Canada, the Canadian Institute for Health Research, Connaught Foundation, and Department of Research at St. Michael Hospital. Dr. Martin O'Donnell is supported by a grant from the CIHR. Dr. Moira Kapral is supported by a New Investigator Award from the CIHR and also received support from the Canadian Stroke Network and the University Health Network Women's Health Program. Dr. Michael Hill is supported by the Heart and Stroke Foundation of Alberta/NWT/NU and the Canadian Institutes for Health Research. These grants were obtained based on competitive applications following publication of grant advertisements. The investigators acted as the sponsors of the study. None of the supporting agencies (HSFC, CSN, CIHR) had input on the design, access to the data, analyses, interpretation, or publication of the study.