Effects of institutional caseload of subarachnoid hemorrhage on mortality: a secondary analysis of administrative data.
OBJECTIVE
Procedures requiring specific skill sets often have been shown to depend on institutional volume, that is, centers receiving a higher volume observe better outcomes in those patients. This relationship recently has been shown to exist for subarachnoid hemorrhage(SAH) patients in a large study in the United States. We aim to examine this relationship for SAH patients in England, restricting analysis to specialist neurosurgical units.


METHODS
Aggregate counts of patients with SAH in 25 specialist neuroscience centers in England, from 2005 to 2011, were obtained from the Hospital Episode Statistics database maintained by the National Health Service Information Center. These data were linked with national mortality statistics to obtain counts of deaths. Poisson regression was used to investigate the relationship between institutional caseload of SAH and 6-month mortality from any cause. Six-month mortality rates and mortality ratios were computed.


RESULTS
Annual institutional caseload of admissions with SAH was inversely related to 6-month mortality (P=0.009; r(2)=0.26). Each 100-patient increase in annual patient volume was associated with a 24% reduction in mortality (adjusted mortality ratio, 0.76; confidence interval, 0.67-0.87). This relationship was consistent across the entire range of annual institutional caseloads examined (29-367 cases for the lowest and highest volumes seen in a single center in 1 year).


CONCLUSIONS
Our results provide support for management of SAH at high-volume centers and suggest that health care policy in this setting should pursue regionalization while ensuring an adequate geographic spread of access to care.
University of Cambridge, Cambridge CB1 8RN, UK. lm509@medschl.cam.ac.uk
Lisa
L
McNeill
Shane W
SW
English
Nicholas
N
Borg
Basil F
BF
Matta
David K
DK
Menon
D004739:England; D005500:Follow-Up Studies; D006739:Hospital Administration / Q000706:statistics & numerical data*; D006760:Hospitalization / Q000706:statistics & numerical data; D061847:Hospitals, High-Volume / Q000706:statistics & numerical data*; D061846:Hospitals, Low-Volume / Q000706:statistics & numerical data*; D006801:Humans; D008137:Longitudinal Studies; D016012:Poisson Distribution; D012189:Retrospective Studies; D013222:State Medicine; D013345:Subarachnoid Hemorrhage / Q000401:mortality*