Consensus Statement on Performance of Carotid Duplex Studies, Gray Scale and Doppler Interpretation Criteria Released

 Should you change your carotid criteria? A new consensus statement on performance of carotid duplex studies, gray scale and Doppler Interpretation criteria has been published. Should you change your protocols and interpretation criteria? Having trouble with correlating your carotid duplex exams with the gold standard?

A multidisciplinary group whose members are considered experts in the field of vascular ultrasound testing has published a consensus statement on the performance of carotid duplex studies and gray scale and Doppler interpretation criteria. “The goal of the conference was to develop recommendations for the performance of Doppler US and Interpretation of the results in the diagnosis of ICA stenosis”. The consensus panel commented on standardization of six specific areas of testing and interpretation.

Technical Considerations:

It is recommended that exams should be performed with gray scale, color Doppler, and spectral Doppler in a standardized manner according to one of the recognized accrediting bodies. The Doppler waveform should be obtained at an angle equal to or less than 60 degrees. Care should be taken placing the sample volume within the ICA so that the should be positioned within the ICA and carried out to it’s distal end so that the Doppler should be positioned within the ICA and carried out to it’s distal end so that the greatest area of stenosis is documented.

Diagnostic Strata, Doppler Diagnostic Thresholds and reporting:

There is lack of standardization reporting criteria apparent between testing centers as well as within some testing centers. Because Doppler is inaccurate for subcategorizing stenosis less than 50% subcategories should not be used. Rather all disease under 50% should be reported as < 50% based on gray scale and Doppler information. The consensus panel recommends testing centers should have uniform criteria that are strictly adhered to. The final report should contain pertinent US findings, comments regarding limitations of study or deviations from usual criteria, comparisons to previous studies in the body of the report, and a conclusion or impression. Stratification of ICA stenosis as follows:

Primary Parameters

Additional Parameters

Degree of stenosis (%)

ICA PSV (cm/sec)

Plaque Estimate (%)*

ICA/CCA PSV Ratio

ICA EDV (cm/sec)

Normal

<125

None

<2.0

<40

<50

<125

<50

<2.0

<40

50-69

125-230

>50

2.0-4.0

40-100

> 70 but < near occlusion

>230

>50

>4.0

>100

Near occlusion

High, low or undetectable

Visible

Variable

Variable

Total occlusion

Undetectable

Visible, no detectable lumen

N/A

N/A

*Plaque estimate (diameter reduction) with gray scale and color Doppler US

Quality Assurance and Reference Standard:

It is recommended that every testing center have a system in place for quality assurance and that internal validations be completed by each testing center. There is lack of standard techniques for measuring ICA stenosis in angiography. It is recommended that the NASCET method of carotid stenosis measurement be used when angiography is used to correlate the carotid duplex exam.

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