Is portable carotid Doppler scanning cost-effective?

Carotid endarterectomy reduces the risk of stroke in symptomatic patients with more than 70% ipsilateral internal carotid stenosis. Colour now duplex Doppler (CFD) ultrasound accurately investigates carotid disease but patients must travel to specialist centres. In order to assess the reliability of a portable continuous wave ultrasound system in screening for internal carotid artery (ICA) stenosis, and the potential cost-effectiveness of a mobile carotid screening service, 85 consecutive patients (170 carotid arteries) attending a Vascular Studies Unit were investigated by CFD by one of two experienced vascular technicians. The carotid arteries were then scanned by a research fellow using portable continuous wave ultrasound equipment. CFD demonstrated carotid stenosis > 50%, or occlusion, in 39 ICAs. The portable equipment failed to detect one of these. However, 8 ICAs were erroneously diagnosed to have 50-99% stenosis due to borderline high peak frequencies of 3.5-4.5 kHz on the portable equipment; and 14 were categorized as occluded on the portable equipment due to absent signals, but CFD showed no disease. The overall sensitivity for detecting disease was 98% with a specificity of 83%. We have calculated that a mobile carotid screening service would cost a total of £26 523 per year in capital and running costs but would reduce the number of patients requiring CFD by 65%, thereby saving a total of and £44 606 in transport costs and CFD; making an overall saving of and £18 083 per year. A mobile carotid screening service for several hospitals in a large conurbation is now planned.