Timothy J Coats1, Richard Loffhagen. 1. Emergency Medicine, Leicester University, Leicester Royal Infirmary, Leicester, UK. t.coats@virgin.net
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.
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.
Authors: Christopher R Carpenter; Adnan M Hussain; Michael J Ward; Gregory J Zipfel; Susan Fowler; Jesse M Pines; Marco L A Sivilotti Journal: Acad Emerg Med Date: 2016-09-06 Impact factor: 3.451
Authors: Bilal Majed; Hélène Zephir; Valérie Pichonnier-Cassagne; Yazdan Yazdanpanah; Philippe Lestavel; Pierre Valette; Patrick Vermersch Journal: Int J Emerg Med Date: 2009-11-19