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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 .

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Tags: Neurologic Vascular Tag this Diagnosis.

Prevalence

Population / CalculatorPrevalence 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

Finding SensitivitySpecificity Comments, Study
Non-contrast Head CT
Duplicate Edit
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

CSF RBCs Edit 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 SensitivitySpecificity Comments, Study
Paralysis Edit 13%97%

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Loss of Consciousness Edit 18%96%

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Photophobia Edit 9%96%

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Altered Mental Status Edit 17%91%

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Neck Stiffness Edit 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 SensitivitySpecificity Comments, Study
Lack of Scotoma Edit 100%7%

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Headache Location
Duplicate Edit
96%29%

not temporal

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Headache Quality
Duplicate Edit
96%25%

not "pressing"

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Nausea Edit 91%39%

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Xanthochromia
Duplicate Edit
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 Edit
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 SensitivitySpecificity Comments, Study
Onset During Exercise Edit 40%65%

or any strenuous activity (e.g. coitus)

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Headache Location
Duplicate Edit
57%62%

occipital

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Headache Quality
Duplicate Edit
62%53%

"exploding"

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Worst Headache Edit 83%36%

at onset

in patients with thunderclap headache

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

No History of Migraine Edit 79%27%

either certain or probable migraines

Study: Cephalalgia. 2002 Jun;22(5):354-60. PMID: 12110111

Xanthochromia
Duplicate Edit
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 Edit
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 Edit
Sensitivity = 50%

7 days post-onset. specificity not assessed

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