Volume 16, Issue 5, September 2015.
Dustin G. Mark, MD, et al.

Introduction: Application of a clinical decision rule for subarachnoid hemorrhage, in combination with
cranial computed tomography (CT) performed within six hours of ictus (early cranial CT), may be able
to reasonably exclude a diagnosis of aneurysmal subarachnoid hemorrhage (aSAH). This study’s
objective was to examine the sensitivity of both early cranial CT and a previously validated clinical
decision rule among emergency department (ED) patients with aSAH and a normal mental status.
Methods: Patients were evaluated in the 21 EDs of an integrated health delivery system between
January 2007 and June 2013. We identified by chart review a retrospective cohort of patients
diagnosed with aSAH in the setting of a normal mental status and performance of early cranial CT.
Variables comprising the SAH clinical decision rule (age >40, presence of neck pain or stiffness,
headache onset with exertion, loss of consciousness at headache onset) were abstracted from the
chart and assessed for inter-rater reliability.
Results: One hundred fifty-five patients with aSAH met study inclusion criteria. The sensitivity of
early cranial CT was 95.5% (95% CI [90.9-98.2]). The sensitivity of the SAH clinical decision rule
was also 95.5% (95% CI [90.9-98.2]). Since all false negative cases for each diagnostic modality
were mutually independent, the combined use of both early cranial CT and the clinical decision rule
improved sensitivity to 100% (95% CI [97.6-100.0]).
Conclusion: Neither early cranial CT nor the SAH clinical decision rule demonstrated ideal
sensitivity for aSAH in this retrospective cohort. However, the combination of both strategies might
optimize sensitivity for this life-threatening disease.