Lisette van Dam

MRI for diagnosis of recurrent ipsilateral DVT 2 27 be attributed to the post-thrombotic syndrome (PTS), considering overlapping symptoms as well as the established association between incomplete thrombus resolution for both PTS and recurrent VTE. 24,25 To date, no published study has focused on the optimal diagnostic management of suspected recurrent ipsilateral DVT in anticoagulated patients. Given the clinical relevance and considering this current ‘evidence free zone’, we decided it was reasonable to allow these patients in the study. The 21% baseline prevalence of confirmed DVT in this patient group reassured us of the importance and validity of that decision. What are the clinical implications of our study? First, MRDTI can now be used for therapeutic management decisions in patients with suspected recurrent ipsilateral DVT. Considering the relatively limited availability of MRI and its associated costs, MRDTI can currently not be suggested to be performed in all patients with suspected recurrent DVT. CUS is sufficient when there are no incompressible vein segments or if a thrombus is detected in a venous segment that was previously not affected by DVT, or that was normalized on a reference CUS. Secondly and equally important, the application of MRDTI in several other settings of notoriously difficult to diagnose acute VTE is now worthwhile evaluating, including upper extremity vein thrombosis 26 , isolated pelvic vein thrombosis in pregnancy 27 , cerebral vein thrombosis 28 and splanchnic vein thrombosis. Strengths of our study include the prospective design, a large number of consecutive patients, near complete follow-up and independent adjudication of suspected endpoints. Moreover, the study was performed across several countries and hospital settings, and both 1.5 and 3.0 Tesla MRI machines of several manufacturers were used. Importantly, two thirds of the study sites had not performed MRDTI before the start of the study. This supports the external validity of our study and the wide applicability of our method and its results. Themain limitation of our study is the absence of a control group. Because this was not a randomized study, we could not compare the safety of MRDTI to the current standard diagnostic approach with CUS nor accurately determine the number of patients in whom anticoagulant treatment was prevented by MRDTI. Based on the reports of the reference CUS performed inpatientswithMRDTI negative for DVT, we estimate this latter number to be up to 19% (57/305) of the total study population, which is a considerable improvement of current practice. Second, although we do not expect a fast normalization of the MRDTI signal in patients with symptom duration exceeding 10 days, we excluded such patients from our study. Therefore, we cannot exclude the possibility of a lower sensitivity of MRDTI in patients with