Lisette van Dam

Cost-effectiveness of MRI for diagnosing recurrent ipsilateral DVT 3 49 that the total health care costs of strategies including MRDTI were comparable or even lower compared to strategies without MRDTI. Savings on treatment costs resulted from the higher specificity of MRDTI and thus less false-positive diagnoses compared to CUS. This was also found in previous publications in which CUS could not exclude recurrent DVT in 30% of patients with suspected recurrent ipsilateral DVT 7,13 , resulting in overtreatment and subsequent risk for major bleeding. Strengths and limitations This study presents a cost-effectiveness model in which detailed estimation of patient-level costs for different diagnostic strategies are calculated. The strength of this analysis is the use of a large patient cohort to estimate the diagnostic accuracy of each test and estimate the true-positive, false-negative, true-negative, and false-positive rate of each of the 10 diagnostic scenarios. Moreover, the original study included an accurate follow-up of the included patients and adjudication of endpoints by an independent committee. Therefore, we believe that this analysis provides an accurate overview of the total health care costs in different diagnostic strategies for a Dutch health care setting. Our model has also limitations especially since the validity and robustness of the model is depending on the impact of uncertainties in key input parameters. First, the results must be interpreted within the framework and limitation of findings of the Theia study. One of these limitations is that Theia study included a relatively limited number of patients resulting in broad confidence interval of the primary outcome. Moreover, this was a management study in which a cohort of patients followed a study algorithm in which they were subjected and treated according the MRDTI result and not according CDR, D-dimer and CUS results. Also, D-dimer levels and CUS results were not available for all patients. Even so, since few limiting exclusion criteria were applied in the Theia study, the presented results of the current study are more generalizable to a broad patient population than those from a randomized controlled trial. Second, accurate mortality estimates could not be obtained from our Theia cohort, as none of the patients died from a missed diagnosis, recurrent fatal-PE or anticoagulant-related bleeding. We therefore estimated these risks from available literature, but this resulted in some counter-intuitive estimates: anticoagulation treatment was optimal even for true negative patients, as the 0.18% decrease in recurrent PE mortality outweighed the 0.07% bleeding mortality from