Coats TJ, Loffhagen R. Diagnosis of subarachnoid haemorrhage following a negative computed tomography for acute headache: a Bayesian analysis.
Eur J Emerg Med 2006;
13:80-3. [PMID:
16525234 DOI:
10.1097/01.mej.0000190277.92731.52]
[Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVES
As access to computed tomography scanning has become easier, patients with a lower probability of serious pathology are being scanned. We asked how many lumbar punctures need to be performed to detect each subarachnoid haemorrhage in these lower-risk patients.
METHODS
Literature review and Bayesian analysis of the application of the data to clinical practice.
RESULTS
A computed tomography scan for acute headache has a negative likelihood ratio of 0.02 if the computed tomography is performed at <12 h, 0.07 at <24 h and 0.18 at >24 h. A low pre-test probability, for example 1 in 20 (5%), and a negative computed tomography at <12 h means that more than 1000 lumbar punctures would be required to detect each subarachnoid haemorrhage.
CONCLUSIONS
In patients who have a low pre-computed tomography probability of subarachnoid haemorrhage and undergo an early computed tomography scan, the risk/benefit ratio of lumbar puncture is unclear. A decision rule (risk stratification system) might improve our ability to help the patient make an informed choice.
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