Enriched administrative data can be used to retrospectively identify all known cases of primary subarachnoid hemorrhage.

ABSTRACT

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.