Benefits and risks of screening people for > 60% asymptomatic carotid stenosis in different prevalence groups: realistic case scenario
| Prevalence (%) | Ultrasound to angiogram to surgery | Ultrasound to MRA to surgery | Ultrasound direct to surgery | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
| Ratio benefit: harm | Net strokes prevented/ 10 000 screened | Strokes or deaths in false positives/ 10 000 screened2-150 | Ratio benefit: harm | Net strokes prevented/ 10 000 screened | Strokes or deaths in false positives/ 10 000 screened2-150 | Ratio benefit: harm | Net strokes prevented/ 10 000 screened | Strokes or deaths in false positives/ 10 000 screened2-150 | |||
| 1 | 0.2 | −27 | 30 | 0.6 | −3 | 7 | 0.1 | −41 | 45 | ||
| 5 | 0.7 | −17 | 29 | 1.6 | 11 | 6 | 0.6 | −23 | 43 | ||
| 10 | 0.9 | −4 | 27 | 2.0 | 28 | 6 | 1.0 | 0 | 41 | ||
| 20 | 1.2 | 21 | 24 | 2.3 | 63 | 5 | 1.5 | 45 | 36 | ||
| 25 | 1.3 | 34 | 23 | 2.4 | 81 | 5 | 1.7 | 67 | 34 | ||
Assumptions: ultrasound sensitivity and specificity 85% each; MRA sensitivity and specificity 85% each; surgical risk of stroke or death=3%; angiographic risk of stroke or death=2%; reduction in risk of ipsilateral stroke for true positive severe stenosis from 11% to 3% over five years.
↵2-150 Number of angiographic or surgical strokes or deaths caused in people who are false positives/10 000 screened.