EBQ:Perry Subarachnoid Haemorrhage Study
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Clinical Question
What is the sensitivity of non-contrast head CT for detecting spontaneous subarachnoid hemorrhage (SAH), when performed on a third-generation CT scanner within 6 hours of headache onset?
Conclusion
Third-generation non-contrast head CT is highly sensitive for detecting spontaneous SAH when performed within 6 hours of headache onset and interpreted by a radiologist experienced in reading head CT.
Major Points
Within 6 hours of headache onset, CT had:
Sens = 100% (95% confidence interval: 97%-100%)
Spec = 100% (99.5%-100%)
For all patients studied, CT had:
Sens = 92.9% (89%-95.5%)
Spec = 100% (99.9%-100%)
Population
ED patients in 11 tertiary care centers
Patient Demographics
- Mean age = 45
- 60% women
Inclusion Criteria
- >15 years old
- Acute headache reaching peak intensity within one hour
- Normal neurologic exam
- CT ordered by the treating physician to rule out SAH
Exclusion Criteria
- Focal neurologic deficits
- Papilledema
- History of SAH
- History aneurysm
- Previous VP shunt
- Brain neoplasm
- Onset of headache >14 days ago
- Recurrent headache (≥3 similar)
- Transfer from outside hospital with confirmed diagnosis of SAH
Interventions
Outcome
Primary Outcomes
- To diagnose SAH based on CT, xanthochromia in CSF, or any RBCs in final tube of CSF collected with positive results on cerebral angiography (digital subtraction, CT, or MR angiography)
Secondary Outcomes
Subgroup analysis
Criticisms
Not all study subjects underwent lumbar puncture, possibly resulting in an underestimation of the rate of false-negative CT. However, investigators endeavored to follow up all subjects at 6 months using medical records and phone calls; no patients contacted received a subsequent diagnosis of SAH. Only 50 patients could not be followed up by these methods. For these 50, review of referrals to neurosurgical centers and coroner reports failed to suggest that any had had a missed SAH.