Subarachnoid Hemorrhage: Sensitivity and Specificity

Introduction: For a decision rule to screen patients with acute headache, see BMJ. 2010 Oct 28;341:c5204. PMID: 21030443 .

Prevalence

Population / Calculator	Prevalence	Comments / Study / Link
Headaches in the emergency department	1%	http://sinaiem.wordpress.com/2007/05/07/sah-update-are-new-ct-scanners-good-enough-to-obviate-the-lp/
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The sensitivity and specificity of findings for Subarachnoid Hemorrhage are listed below. See the left navigation bar to change the display.

Sensitive and Specific Findings

92%

100%

patients presenting to ED with sever sudden-onset HA

Sensitivity lower for subarachnoid blood confined to the posterior fossa or spinal cord.

Study: J Emerg Med. 2008 Apr;34(3):237-51. PMID: 18155383

91%

85%

for specificity (i.e. vs traumatic tap), number is for >400/ul. Sensitivity is from 12-24 hours after onset.

Study: Neurocrit Care. 2005;2(2):99-109. PMID: 16159051

Specific Findings

Finding	Sensitivity	Specificity	Comments, Study
Paralysis	13%	97%	in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Loss of Consciousness	18%	96%	in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Photophobia	9%	96%	in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Altered Mental Status	17%	91%	in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Neck Stiffness	61%	90%	in patients with thunderclap headache alternate numbers: sens 30% spec 95% (BMJ. 2010 Oct 28;341:c5204. PMID: 21030443) Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Sensitive Findings

Finding	Sensitivity	Specificity	Comments, Study
Lack of Scotoma	100%	7%	in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Headache Location Duplicate	96%	29%	not temporal in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Headache Quality Duplicate	96%	25%	not "pressing" in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Xanthochromia Duplicate	Sensitivity = 89%		by visual inspection. 12-24 hours after onset. specificity not assessed Study: Neurocrit Care. 2005;2(2):99-109. PMID: 16159051
Non-contrast Head CT Duplicate	Sensitivity = 85%		3-days post onset. specificity not assessed Study: J Emerg Med. 2008 Apr;34(3):237-51. PMID: 18155383

Poorly Diagnostic Findings

Finding	Sensitivity	Specificity	Comments, Study
Onset During Exercise	40%	65%	or any strenuous activity (e.g. coitus) Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Headache Location Duplicate	57%	62%	occipital in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Headache Quality Duplicate	62%	53%	"exploding" in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Worst Headache	83%	36%	at onset in patients with thunderclap headache Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
No History of Migraine	79%	27%	either certain or probable migraines Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111
Xanthochromia Duplicate	Sensitivity = 65%		by visual inspection. 6-12 hours after onset. specificity not assessed. Study: Neurocrit Care. 2005;2(2):99-109. PMID: 16159051
Xanthochromia Duplicate	Sensitivity = 57%		by visual inspection. 4-6 hours after onset. specificity not assessed Study: Neurocrit Care. 2005;2(2):99-109. PMID: 16159051
Non-contrast Head CT Duplicate	Sensitivity = 50%		7 days post-onset. specificity not assessed Study: J Emerg Med. 2008 Apr;34(3):237-51. PMID: 18155383