Increased Intracranial Pressure: Likelihood Ratios

Introduction: It is contraindicated to perform a lumbar puncture on a patient with increased intracranial pressure because of the danger of herniation. The gold standard test for elevated ICP is CT scan.

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The likelihood ratios of findings for Increased Intracranial Pressure are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)

Good Positive Likelihood Ratio
Finding	Result	+LR	-LR
[ + ] Papilledema	+ 0 -	11.1	0.9
by emergency medicine residents in the ED gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758
[ + ] Focal Neurological Signs	+ 0 -	4.3	0.6
gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758
[ + ] History of CNS Mass	+ 0 -	3.7	0.9
gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758

Poorly Diagnostic Findings
Finding	Result	+LR	-LR
[ + ] History of Head Trauma	+ 0 -	0.7	1
Within last 72 hours (Note: NOT DIAGNOSTIC!) gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758
[ + ] History of Seizure	+ 0 -	1.4	0.9
Within last 72 hours gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758
[ + ] History of HIV	+ 0 -	1.2	1
HIV positivity gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758
[ + ] Immunosuppressed	+ 0 -	1.6	0.8
gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758

Good Positive and Negative Likelihood Ratios
Finding	Result	+LR	-LR
[ + ] Clinical diagnosis	+ 0 -	18.8	0
i.e. based on abnormal findings on history or physical exam gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758
[ + ] Papilledema	+ 0 -	4.7	0.2
by ophthalmologists viewing a picture of a stereoscopic view of a dilated eye Study: J Fam Pract. 1991 Oct;33(4):381-6. PMID: 1919455
[ + ] Altered Mental Status	+ 0 -	2.2	0.4
gold standard is CT (? is LP contraindicated) Study: Arch Intern Med. 1999 Dec 13-27;159(22):2681-5. PMID: 10597758
[ + ] Papilledema	+ 0 -	3.8	0.5
by family practitioners viewing a picture of a stereoscopic view of a dilated eye Study: J Fam Pract. 1991 Oct;33(4):381-6. PMID: 1919455