This is the protocol for a review and there is no abstract. The objectives are as follows:
To estimate the sensitivity and specificity of duplex ultrasound for the detection of distal and proximal DVT in symptomatic patients with prior testing by a clinical prediction rule (with or without additional D-dimer testing).
The accuracy of ultrasound for DVT may be affected by body mass index and whether the patient has had a previous DVT. If possible, we shall investigate both previous DVT and body mass index as possible sources of heterogeneity, but recognise that these are patient-specific rather than study-specific characteristics. This means that results reported at the study level, for example average body mass index, may not be informative in an analysis and are more appropriately investigated with individual patient data. However, such an analysis may be possible if studies report results stratified by previous DVT status or body mass index. Two study-specific characteristics we shall investigate are the generation of the technology of the ultrasound scanner and type of reference standard: ascending venography, CT venography, or MR venography. Moreover, as the accuracy of duplex ultrasound depends on whether the DVT is distal or proximal, we shall perform separate meta-analyses according to site.