Lisette van Dam

Chapter 4 70 diagnostic management studies should be evaluated is the percentage of patients with VTE during 3 months of follow-up despite a normal venography finding. 17 There are limited data on the utility of D-dimer testing in patients with suspected recurrent DVT while on anticoagulant treatment. 17 It was previously shown that the D-dimer concentration decreases during anticoagulant therapy, which leads to a decrease in sensitivity from 96% to 89%. 18 This was confirmed in our analysis: the sensitivity of the Wells rule/D-dimer combination decreased from 97% to 86% in patients on anticoagulant therapy. Strengthsof the studyare theprospectivedesign, the large sample size, theaccurate follow-up of the included patients as well as the adjudication of the endpoints by an independent committee. Also, the study included university and non-university hospitals from several European countries, and different quantitative D-dimer assays were used, all contributing to the external validity of our findings. The main limitation of this analysis is that patients were not managed according the results of CDR and D-dimer testing. Also, D-dimer levels were not available for all patients. Due to the limited number of study patients our data should be considered to be hypothesis generating. Future studies with a larger study cohort, including an upfront determined sample size calculation are needed. In conclusion, although the sensitivity of the (modified) Wells rule in combination with D-dimer testing was sufficient as predefined in the Theia study protocol, we observed a 6.1% diagnostic failure-rate. Importantly, the combination of an unlikely CDR and normal D-dimer test was only present in 21% of patients when using the original Wells rule, and 14%when using the modified Wells rule. Our data do not support routine assessment of CDR and D-dimer in the diagnostic workup of suspected recurrent (ipsilateral) DVT. Based on the results of our analysis we suggest imaging in all patients with suspected recurrent (ipsilateral) DVT starting with CUS and a MRDTI scan in patients with an abnormal or inconclusive CUS result.