Carotid bruit for detection of hemodynamically significant carotid stenosis: the Northern Manhattan Study
Elizabeth V Ratchford1, Zhezhen Jin, Marco R Di Tullio
1Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, USA. eratchf@jhmi.edu
Insights
Carotid auscultation has low sensitivity for detecting carotid stenosis, with a high false-negative rate. Ultrasonography is recommended for high-risk patients, regardless of bruit presence.
Area of Science:
- Vascular Medicine
- Diagnostic Accuracy
- Epidemiology
Background:
- Carotid bruits are physical examination findings, but their prevalence and predictive value for carotid stenosis are not well-established.
- Carotid stenosis is a significant risk factor for stroke.
Purpose of the Study:
- To determine the prevalence of carotid bruits in a multiethnic cohort.
- To evaluate the diagnostic accuracy of auscultation for detecting hemodynamically significant carotid stenosis using carotid duplex as the gold standard.
Main Methods:
- Prospective, multiethnic, community-based cohort study (Northern Manhattan Study - NOMAS).
- Included 686 stroke-free subjects who underwent carotid auscultation and carotid duplex.
- Assessed prevalence of carotid bruits and diagnostic metrics (sensitivity, specificity, PPV, NPV, accuracy) for stenosis detection.
Main Results:
- Prevalence of >=60% carotid stenosis was 2.2%; prevalence of carotid bruits was 4.1%.
- Auscultation sensitivity was 56%, specificity 98%, positive predictive value (PPV) 25%, negative predictive value (NPV) 99%, and accuracy 97.5% for detecting stenosis.
- A 44% false-negative rate was observed for auscultation.
Conclusions:
- The prevalence of carotid bruits and significant carotid stenosis was low in this cohort.
- Auscultation has low sensitivity and PPV for detecting carotid stenosis, making it insufficient to rule out the condition.
- Carotid duplex ultrasonography should be considered for high-risk asymptomatic patients, irrespective of auscultation findings.
Objective:
The prevalence of carotid bruits and the utility of auscultation for predicting carotid stenosis are not well known. We aimed to establish the prevalence of carotid bruits and the diagnostic accuracy of auscultation for detection of hemodynamically significant carotid stenosis, using carotid duplex as the gold standard.
Methods:
The Northern Manhattan Study (NOMAS) is a prospective multiethnic community-based cohort designed to examine the incidence of stroke and other vascular events and the association between various vascular risk factors and subclinical atherosclerosis. Of the stroke-free cohort (n=3298), 686 were examined for carotid bruits and underwent carotid duplex. Main outcome measures included prevalence of carotid bruits and sensitivity, specificity, positive predictive value, negative predictive value and accuracy of auscultation for prediction of ipsilateral carotid stenosis.
Results:
Among 686 subjects with a mean age of 68.2 +/- 9.4 years, the prevalence of >/=60% carotid stenosis as detected by ultrasound was 2.2% and the prevalence of carotid bruits was 4.1%. For detection of carotid stenosis, sensitivity of auscultation was 56%, specificity was 98%, positive predictive value was 25%, negative predictive value was 99% and overall accuracy was 97.5%.
Discussion:
In this ethnically diverse cohort, the prevalence of carotid bruits and hemodynamically significant carotid stenosis was low. Sensitivity and positive predictive value were also low, and the 44% false-negative rate suggests that auscultation is not sufficient to exclude carotid stenosis. While the presence of a bruit may still warrant further evaluation with carotid duplex, ultrasonography may be considered in high-risk asymptomatic patients, irrespective of findings on auscultation.
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