Lisette van Dam

Chapter 3 42 repeated diagnostic testing (i.e. return diagnostic costs) would be the same as at initial presentation, except for the following scenarios: a) in scenarios including CDR assessment and D-dimer testing and radiologic imaging (CUS and/or MRDTI) were only repeated radiological testing would be performed and b) in scenarios including MRDTI after CUS were only repeated CUS would be performed. And thirdly, we assumed that all patients with an initial false-negative diagnosis would have a true-positive diagnosis at the repeated diagnostic testing and thus included treatment costs as for models were a true-positive diagnosis was made. The mortality risk included three types of mortality: 1) mortality frommisdiagnosis, 2) from recurrent fatal PE and 3) from anticoagulant-related bleeding.1) For the mortality risk associated with misdiagnoses, we considered the probability of death for the time period between the false-negative diagnosis and the moment of the true-positive diagnosis, using the exact timelines observed in the Theia study. This was estimated as a fixed 2.05% of the number of false-negative diagnoses, i.e. obtained from previous publications that 50% of the patients with DVT would have asymptomatic PE and 4.1% of all PEs is fatal 26-30 . 2) The mortality risk as a result of recurrent fatal PE during 1-year follow-up period was calculated for patients with a false-positive, true-positive or initial false-negative and true-negative diagnosis. 2a) The risk for mortality from recurrent fatal PE in patients with a false-positive diagnosis was set as 0.0%, as the risk for fatal PE in patients with no recurrent DVT at baseline, but who were falsely treated with anticoagulants is estimated to be negligible. 2b) The risk for mortality from recurrent fatal PE during anticoagulant treatment in patients with a true-positive diagnosis and an initially false-negative diagnosis was set at 0.07%, which was obtained from previous publications. 25 2c) Mortality as result of recurrent fatal PE in true-negative patients without anticoagulant treatment was estimated as 0.18%, also obtained from previous studies. 31,32 3) The mortality risk as a result of bleeding related to anticoagulant treatment was estimated as 0.07% of the number of those treated with anticoagulants (i.e. true-positives, false-negatives and false-positives), including 0.06% among DOAC users versus 0.17% among VKA users. 25 For each diagnostic scenario, the estimated 1-year health care costs were plotted against the estimated mortality. Diagnostic scenarios with costs and mortality equal or higher than other scenarios were not considered cost-effective. 33 The remaining scenarios constitute the efficient frontier, i.e. the set of potentially most cost-effective strategies. For these scenarios incremental cost ‐ effectiveness ratios (ICERs) were calculated, defined by the difference in costs divided by the difference in mortality. The estimated costs per-prevented-death ratios were used