Carotid duplex ultrasonography: Importance of standardisation
Byrd S., Robless P., Baxter A., Emson M., Halliday A.
Background. Carotid duplex ultrasonography (CDUS) is an established non-invasive tool for assessing patients with suspected carotid bifurcation disease. Current trends show an increased dependence on CDUS in recommending patients for stroke prevention surgery. The aim of the study was to evaluate routine practice in vascular laboratories across 26 countries participating in The Asymptomatic Carotid Surgery Trial (ACST), and to determine the areas which are in need of future standardisation if CDUS is to be the primary tool in recommending patients for CEA. Methods. Retrospective. Information was gathered from questionnaires, and 22 on-site visits of vascular laboratories between August 1996 to September 1997. Setting. Clinical vascular laboratory practice. Participants. Eligible participants were vascular laboratories of ACST collaborators. Measures. Laboratories were compared in 7 categories: ultrasound equipment, operators, experience, protocols, stenosis evaluation, interpretation criteria, and reporting. Results. Information on 117 respondents showed that (i) experience: at least one operator in each laboratory had more than 3 years experience; (ii) equipment: 88% (103/117) had colour duplex capability; (iii) operators: 54% of laboratories had exams performed by technologists, 33% vascular surgeons, 28% radiologists, and 35% other. The most significant findings were in (iv) stenosis evaluation: only 29% (33/117) were using a standardised Doppler angle (this single factor may greatly alter exam results); and (v) interpretation criteria; with >41 different criteria reported. These specific laboratory variations can affect those patients considered appropriate for CEA. Conclusions. This study highlights the most significant areas for future standardisation to be Doppler angle and interpretation criteria, if CDUS is to be a primary tool in recommending patients for CEA, when indicated by clinical trial results.