--- You wrote:
My medical director wanted to post this question:  What criteria are other
labs using to identify 60% stenosis in the ICA, 70% stenosis, and 80%
stenosis?  Any input would be greatly appreciated.
--- end of quote ---
In compiling our QA for ICAVL many years ago, we observed that we were over-estimating the % stenosis, particularly at the 50% breakpoint.  This led to an analysis of our velocity data compared to angio measurements (we use the NASCET method of measurement which compares the stenosis to the more distal diameter of a normal segment of the internal carotid artery).
In the process, we observed (as have many others) that there are significant differences in velocity measurements among different brands of scanners.
Also, because of the NASCET and ACAS studies, we wanted to see what our breakpoints were for 60% and 70% stenoses.
The result is that we developed PSV, EDV, and ICA/CCA ratio criteria for 50, 60, 70, and 80% breakpoints for two different models of scanners.
I'm happy to share our current DHMC velocity criteria tables, but also must caution that these were developed for 2 particular models of scanners and that they should be validated in your own setting with your own scanners.
(If you use another brand or model of scanner, try to find published material that uses the same kind of scanner for a good starting point for your QA analysis.
Maybe others will share their criteria tables on Flownet.)
Note:  All the following > than symbols should really be "greater than or equal to" symbols, but I don't have that option.  And all velocities are cm/sec.
For the Siemens Q2000:
50-60%  PSV > 165, EDV > 65, ICA/CCA ratio > 2.5
60-70%  PSV > 200, EDV > 80, ICA/CCA ratio > 3.1
70-80%  PSV > 240, EDV > 100, ICA/CCA ratio > 3.9
>80%     PSV > 290, EDV > 130, ICA/CCA ratio > 4.8
For the ATL3000:
50-60%  PSV > 220, EDV > 79, ICA/CCA ratio > 3.2
60-70%  PSV > 275, EDV > 98, ICA/CCA ratio > 4.2
70-80%  PSV > 340, EDV > 122, ICA/CCA ratio > 5.6
>80%     PSV > 430, EDV > 151, ICA/CCA ratio > 7.5

If all 3 parameters fall into one category, we go ahead and report the stenosis in the 10% increment.  However, often, the 3 criteria span two or even three ranges.
In that case, we report a wider range, eg. 50-79% or 60-79%.
As we get new scanners in our lab, we may find that adjustments have to be made.
Long live QA!
The article by Mark Fillinger that MaryAnne referred to can be found in the Journal of Vascular Surgery, 24(5): 856-64, November 1996.
"Carotid duplex criteria for a 60% or greater angiographic stenosis: variation according to equipment."
If anyone looks at data with these numbers, I'd love to hear how they work for your lab.
Thanks,
Anne Musson, RVT
Dartmouth-Hitchcock Medical Center
Lebanon, New Hampshire