Lisette van Dam

Chapter 3 38 would have been started in case of a MRDTI positive for DVT. In the second scenario, all patients would have been referred for CUS, which was either normal or abnormal, and anticoagulant treatment would have been started in case of an abnormal CUS. In the third scenario, CUS would have been performed in all patients, but the results were judged as positive/negative/inconclusive and anticoagulant treatment would have been started in patients with a positive or inconclusive CUS. In the fourth scenario, all patients would have been referred for CUS and MRDTI would be performed in case of an abnormal CUS. Anticoagulant treatment would have been started in patients with a MRDTI positive for recurrent DVT. In the fifth scenario, CUS would have been performed in all patients and only patients with an inconclusive CUS would have been referred for MRDTI. Anticoagulant treatment would have been started based on a positive MRDTI or positive CUS result. In scenario 6 to 10, the combination of CDR assessment and D-dimer testing was added as initial step to scenario 1 to 5. Diagnostic imaging (CUS and/or MRDTI) would only be performed in patients with a likely clinical probability and/or abnormal D-dimer result. Definitions A likely clinical probability according the Wells rule was defined as a Wells score of ≥ 2 points. 16 An abnormal D-dimer test was defined as abnormal according the assay dependent threshold, because this differed between the various assays used in the Theia study. An evaluation of the diagnostic performance of the Wells rule and D-dimer testing in the Theia study was recently published. 17 A normal CUS was defined as full compressibility along the venous system. An abnormal CUS was defined as 1 or more non-compressible venous segments. A positive CUS was defined as a new non-compressible segment or a ≥ 2-4 mm increase in vein diameter of a previously non-compressible venous segment when compared to a reference CUS. A negative CUS was defined as the absence of a non-compressible segment or the absence of a new non-compressible segment in comparison with a reference CUS and a < 2 mm increase in vein diameter of a previously non- compressible vein. An inconclusive CUSwas defined as 1 ormore non-compressible venous segment(s) in the absence of a reference CUS for comparison. An MRDTI scan positive for acute DVT was defined as a high signal intensity in the location of a deep vein against the suppressed background greater than that observed in the contiguous segments or corresponding ipsilateral vein. Major bleeding