Carotid Artery Stenosis: Likelihood Ratios

Introduction: Plaque in the carotid artery can cause stenosis leading to hemodynamic compromise. This is clinically relevant mostly as it applies to an increased risk of Stroke, which can be reduced by a carotid endarterectomy in certain indications (i.e. with a threshold degree of stenosis).

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The likelihood ratios of findings for Carotid Artery Stenosis 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 and Negative Likelihood Ratios
Finding	Result	+LR	-LR
[ + ] Carotid Bruit	+ 0 -	3.7	0.4
>50% stenosis. in patients referred for carotid ultrasound (bias?) Study: BMC Neurol. 2008 Jun 24;8:23. PMID: 18577216
[ + ] Doppler Ultrasound	+ 0 -	2.1	0.5
carotid doppler evaluating Peak Systolic Velocity (PSV), for criteria consistent with >70% stenosis. data from NASCET trial Study: Stroke. 1995 Oct;26(10):1747-52. PMID: 7570719

Good Positive Likelihood Ratio
Finding	Result	+LR	-LR
[ + ] Carotid Bruit	+ 0 -	5.6	0.8
for stenosis >50%. in asymptomatic patients undergoing CABG Study: Int J Cardiol. 2006 Feb 15;107(2):225-9 PMID: 16412801

Poorly Diagnostic Findings
Finding	Result	+LR	-LR
[ + ] Carotid Bruit	+ 0 -	1.6	0.6
stenosis >70%. symptomatic patients (TIA or stroke) Study: Ann Intern Med. 1994 Apr 15;120(8):633-7. PMID: 8135446