To evaluate the accuracy of duplex ultrasound (DUS) for graft surveillance after peripheral arterial bypass grafting using autologous vein.

The accuracy of DUS may be affected by the training and experience of the person undertaking the test (Brunkwall 2009), the age of the patient, the age of the graft, the type of reference standard used and the year of publication. We shall investigate the first two (background of the person conducting the ultrasound examination and age of patient) as sources of heterogeneity using statistical methods. The remaining factors will be examined graphically. The type of reference standard will also be used in sensitivity analyses.