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Updated: Apr 3, 2026
Double Direct Injection of Blood into the Cisterna Magna as a Model of Subarachnoid Hemorrhage
Published on: August 30, 2020
Enriched administrative data can be used to retrospectively identify all known cases of primary subarachnoid
Shane W English1, Lauralyn McIntyre1, Dean Fergusson2
1Department of Medicine (Critical Care), The Ottawa Hospital, Ottawa, Canada; Ottawa Hospital Research Institute, Clinical Epidemiology Program, University of Ottawa, Ottawa, Canada.
Objective:
We derived and validated a method to screen all hospital admissions for 1° subarachnoid hemorrhage (SAH) by retrospectively implementing recognized diagnostic criteria.
Study Design And Setting:
A screen for 1° SAH was developed using two previously created registries. Screen-positive cases underwent diagnosis confirmation with primary record review. A review of all patient hospital encounters with the diagnostic code for 1° SAH, and cross-referencing with an existing SAH registry was undertaken to identify missed cases.
Results:
Three subscreens were combined to form the 1° SAH screen (sensitivity: 98.4% [95% CI: 91.7-99.7%], specificity: 93.4% [95% CI: 90.4-95.4%], n = 455 patients in validation sample). From 1,699 screen-positive admissions between July 1, 2002 and June 30, 2011, we identified 831 true cases of SAH of which 632 patients had 1° SAH from ruptured aneurysm/arteriovenous malformation (sensitivity: 96.5% [95% CI: 94.8-97.8%], specificity: 40.3% [95% CI: 38.1-42.6%]). A review of all encounters with a diagnostic code for 1° SAH yielded additional 22 true cases.
Conclusion:
When positive, our 1° SAH screen significantly increases the probability of this diagnosis in a particular hospitalization. The addition of patient hospitalizations encoded with the diagnostic code for 1° SAH improved sensitivity. Together, these methods represent the best way to retrospectively identify all cases of 1° SAH within an extensive sampling frame.
