Twenty-one studies (data for 2,895 scan pairs) were included in the review. Overall quality scores ranged from 11 to 14. Items that scored no or unclear were blinded interpretation of the index test and/or reference standard (four studies) and avoidance of differential verification bias (one study).
Pooled sensitivity for unenhanced duplex ultrasound (n=2,610) was 0.77 (95% CI 0.64 to 0.86, I2=82%). Pooled specificity was 0.94 (95% CI 0.88 to 0.97, I2=90%).
Pooled sensitivity for contrast-enhanced ultrasound (n=285), was 0.98 (95% CI 0.90 to 0.99; I2=32%). Pooled specificity was 0.88 (95% CI 0.78 to 0.94, I2=67%).
Sensitivity analysis that excluded the study with the lowest quality score did not change results. There was no evidence of publication bias.