Lisette van Dam

Chapter 2 16 METHODS Study design and patients The Theia study was a prospective international multicenter diagnostic management study conducted at five academic and seven non-academic teaching hospitals across five countries. From March 2015 to March 2019, we included patients aged 18 years or older with clinically suspected acute recurrent ipsilateral DVT of the leg. Exclusion criteria were DVT diagnosed by CUS within six months before presentation (to prevent false positive MRDTI findings because of a previous recent DVT episode 15 ), symptom duration of more than ten days, suspected concurrent acute pulmonary embolism (PE), hemodynamic instability at presentation (as a consequence of concurrent PE or other clinical conditions), medical or psychological condition not permitting completion of the study or signing informed consent (including life expectancy less than three months) and general contraindications for MRI. Furthermore, patients treated with full-dose anticoagulation that had been initiated ≥ 48 hours before the eligibility assessment were excluded. Notably, from August 2015 onwards, patients with suspected recurrent DVT while receiving therapeutic anticoagulant treatment ≥ 48 hours were also allowed in the study as they were found to represent a high proportion of the screened study population (30%) in the first year after study initiation and thus formed a clinically relevant patient group. The study protocol and its amendments were approved by the institutional review board of the Leiden University Medical Center (LUMC) Leiden, the Netherlands; for all participating hospitals in the Netherlands), by the institutional review board at the Danderyd Hospital (Stockholm, Sweden), Østfold Hospital (Østfold, Norway), the Ottawa Hospital (Ottawa, Canada) and Rambam Health Care Campus (Haifa, Israel). All patients provided written informed consent. All participating centers were provided with a training set of MRDTI images and performed a test MRDTI prior to study start. The study was only initiated if the quality of this scan was judged adequate by the LUMC radiologists’ expert team. The study was designed by the authors with no involvement of any commercial entity. The authors vouch for the accuracy and completeness of the data and analyses and for the fidelity of the study to the protocol. No one who is not an author contributed to the writing of the manuscript.