Lisette van Dam

Chapter 3 36 METHODS Study population This study was a predefined secondary analysis of the Theia study (NCT02262052), a prospective international multicenter outcome study in which we evaluated the safety of excluding recurrent ipsilateral DVT with MRDTI. The full details of the study design and outcomes have been described previously. 13 In summary, between March 2015 to May 2019 adult patients with suspected recurrent ipsilateral proximal DVT of the lower extremity on or off anticoagulant treatment were managed according the result of the MRDTI scan. Main exclusion criteria were suspected concomitant acute PE, CUS-proven acute DVT within 6 months of presentation and general contra-indications for magnetic resonance imaging. CUS was performed as a reference examination in all patients with a MRDTI negative for DVT to guide diagnostic testing if suspected recurrence occurred during follow- up. Furthermore, the protocol dictated CDR assessment using the original Wells rule and D-dimer testing in all patients. Importantly, CUS, CDR assessment and D-dimer results did not influence management decisions. All included patients were followed for a 3-month period for the occurrence of recurrent VTE (DVT or PE), anticoagulation-associated major bleeding and all-cause mortality. For the current analysis, the results of the Theia study were extrapolated to the Dutch situation, excluding patients who were on anticoagulant treatment ≥ 48 hours prior to inclusion. Study objectives and outcomes The aimof this analysis was to compare the health care costs between 10 diagnostic scenarios for the diagnostic management of suspected recurrent ipsilateral DVT, in relation to the associated mortality. The scenarios included CDR assessment according to the Wells criteria in combination with D-dimer testing, and diagnostic imaging with CUS and/or MRDTI ( Figure 1 ). In the scenarios including CUS, results were defined as either normal/abnormal or positive/negative/inconclusive; the latter is only applicable if a reference CUS was available. 15 The first five scenarios included only diagnostic imaging tests. In the first scenario, MRDTI would have been performed in all patients and anticoagulant treatment