This 2015 paper retrospectively reviews the sensitivity of CT for SAH. I’m also including a link to a 2011 prospective study that demonstrates similar findings. And for good measure, I’ve included a link to the ACEP clinical policy on headache. It’s a little out dated (2009) but it’s the most current guideline we have for our speciality.
1. Blok KM, Rinkel GJ, Majoie CB, Et. Al. CT within 6 hours of headache onset to rule out subarachnoid hemorrhage in nonacademic hospitals. Neurology. 2015 May 12;84(19):1927-32. doi: 10.1212/WNL.0000000000001562. Epub 2015 Apr 10.
To investigate whether staff radiologists working in nonacademic hospitals can adequately rule out subarachnoid hemorrhage (SAH) on head CT <6 hours after headache onset.
In a multicenter, retrospective study, we studied a consecutive series of patients presenting with acute headache to 11 nonacademic hospitals. Inclusion criteria were (1) normal level of consciousness without focal deficits, (2) head CT <6 hours after headache onset and reported negative for the presence of SAH by a staff radiologist, and (3) subsequent CSF spectrophotometry. Two neuroradiologists and one stroke neurologist from 2 academic tertiary care centers independently reviewed admission CTs of patients with CSF results that were considered positive for presence of bilirubin according to local criteria. We investigated the negative predictive value for detection of SAH by staff radiologists in nonacademic hospitals on head CT in patients scanned <6 hours after onset of acute headache.
Of 760 included patients, CSF analysis was considered positive for bilirubin in 52 patients (7%). Independent review of these patients’ CTs identified one patient (1/52; 2%) with a perimesencephalic nonaneurysmal SAH. Negative predictive value for detection of subarachnoid blood by staff radiologists working in a nonacademic hospital was 99.9% (95% confidence interval 99.3%-100.0%).
Our results support a change of practice wherein a lumbar puncture can be withheld in patients with a head CT scan performed <6 hours after headache onset and reported negative for the presence of SAH by a staff radiologist in the described nonacademic setting.
© 2015 American Academy of Neurology.
2. Perry JJ, Stiell IG, Sivilotti ML, et. al. Sensitivity of computed tomography performed within six hours of onset of headache for diagnosis of subarachnoid haemorrhage: prospective cohort study. BMJ. 2011 Jul 18;343:d4277. doi: 10.1136/bmj.d4277.