IAC, for every good reason, requires that the same criteria be used by all practitioners in the same lab, whether those criteria are in-house derived and validated, or one of the many published criteria sets. In-house derived (and validated) data is, in my view, likely to be more accurate and useful, but not possible in all settings. I am not aware of any published carotid stenosis criteria which are specific to the 10% range which offer acceptable accuracy. To make criteria acceptable to varying lab specifics, and because of the vagaries of how the measurement data can be derived, fairly broad ranges end up being the most predictable. That said, I know of labs which have established (and validated) tighter ranges; I haven't seen that those conditions can be applied to other institutions, generally.
BTW, I am in need of enlightenment: I have seen, here and other places, the term "NASCET criteria" used and I don't know of any carotid stenosis criteria published as part of the North American Symptomatic Endarterectomey
Trial papers. NASCET changed the measurement technique (distal carotid as the denominator) which virtually everybody (many grudgingly) eventually adopted, but NASCET used angiography, not US, as the measurement methodology; so help me, someone: what are the "NASCET criteria"?