Lisette van Dam

Chapter 2 28 longer or unknown duration of symptoms. Furthermore, 29% of patients with MRDTI negative for DVT were on anticoagulants at inclusion and continued this during the follow-up period and were thus largely protected from recurrent VTE. By analyzing the patients without any anticoagulant treatment during follow-up separately, we have corrected for this potential bias. Moreover, the high number of patients on anticoagulant treatment presenting with suspected recurrent DVT and their high 21% baseline prevalence of recurrent DVT support the decision to include these patients, especially in regard to the lack of evidence of diagnostic and therapeutic management of this patient subgroup. Lastly, we had estimated that 246 patients with MRDTI negative for DVT would be necessary to reject the null hypothesis. Due to the baseline prevalence of recurrent DVT being higher than anticipated and the inclusion of patients on anticoagulant treatment, this number was not met. The sample size was not adjusted as this was not anticipated in the study protocol and due to feasibility after study initiation. Nevertheless, the upper limit of the 95%CI of the primary endpoint in patients with MRDTI negative for DVT left untreated remained well below the predetermined safety threshold. Furthermore, according a recent statement of the Scientific and Standardization Committee of the International Society on Thrombosis and Haemostasis, our observed low rate of diagnostic failures in the perspective of the high baseline DVT prevalence underlines the safety of ruling out recurrent ipsilateral DVT by MRDTI. 29 In conclusion, the incidence of VTE recurrence after negativeMRDTI was low. MRDTI proved to be a simple, feasible and reproducible diagnostic test. We suggest, that MRDTI can now be considered for therapeutic management decisions in patients with suspected recurrent ipsilateral DVT and an inconclusive compression ultrasound result. Furthermore, MRDTI creates new opportunities for accurate diagnosis in other challenging settings of suspected acute venous thrombosis.