Lisette van Dam

Chapter 4 66 Primary outcome Among the 231 patients who were not treated with anticoagulants, 119 patients (52%) had an unlikely CDR according to the original Wells rule, 66 patients (29%) had a normal D-dimer test and 49 patients (21%) had a combination of an unlikely CDR and a normal D-dimer test. All results of the combination of CDR assessment and D-dimer testing are presented in Appendix A . Three of 49 patients (6.1%; 95%CI 1.3-18%) with an unlikely original Wells score and a normal D-dimer test had recurrent DVT at baseline or during 3-month follow-up ( Table 3 ). The combination of the original Wells rule and D-dimer test yielded a sensitivity of 97% (95%CI 92- 99%) and specificity of 36% (95%CI 28-45%). When using the modified Wells rule in combination with D-dimer testing, 3 of the 28 patients (11%; 95%CI 2.2-31%) with an unlikely CDR and a normal D-dimer test had recurrent DVT at baseline or during 3-month follow-up. The sensitivity was 97% (95%CI 92-99%) and the specificity was 20% (95%CI 14-27%). Secondary outcomes The incidence of recurrent DVT in patients treated with anticoagulants at baseline who had an unlikely probability according to the original Wells rule in combination with a normal D-dimer test was 2 of 30 patients (6.7%; 95%CI 0.81-24%) ( Table 3 ). The sensitivity and specificity of the combination of an unlikely probability by the original Wells rule and a normal D-dimer test for acute recurrent DVT were 86% (95%CI 60-96%) and 56% (95%CI 42-69%), respectively. When applying the modified Wells rule, the sensitivity was 93% (95%CI 69-99%) and the specificity was 32% (95%CI 21-46%). The number of required diagnostic imaging tests in the different scenarios for the diagnostic work up of suspected recurrent DVT are shown in Table 4 . Depending on the diagnostic scenario, CUS was needed in 71-100% of patients and MRDTI in 33-100% of patients. When CDR assessment in combination with D-dimer testing was applied before diagnostic imaging, CUS was needed in 71-83% of patients and MRDTI in 33-83% of patients.