Facts and Misfacts on <scp>D</scp> ‐Dimer Testing. Consensus Guidance From the Italian Society on Thrombosis and Hemostasis ( <scp>SISET</scp> )

D-dimer defines degradation products derived from the proteolysis mediated by plasmin on cross-linked fibrin. The evidence-based use of D-dimer in some conditions has been consolidated. Currently, however, there is an entrenched prescription of D-dimer testing to screen otherwise healthy subjects that may induce prescribing physicians to start time-consuming diagnostic procedures that may generate patient anxiety/distress and often fail to reach meaningful conclusions for patients' management. To make things worse, the incidental finding of unexplained elevated D-dimer is often, and inadvertently, taken as an index of venous thromboembolism (VTE) that may induce unnecessary initiation of thromboprophylaxis. Finally, population studies showed that elevated D-dimer is variably associated with arterial thrombosis. However, the above studies do not allow establishing a direct causal relationship between elevated D-dimer and disease, which makes D-dimer measurement hardly applicable in individual patients. With this as background, the Italian Society on Thrombosis and Hemostasis appointed a panel to prepare a guidance on the use of D-dimer based on the literature and expert opinion. The main conclusions of the panel can be summarized as follows: (i) D-dimer can be reliably used in combination with pre-test clinical probability to exclude VTE in symptomatic outpatients. (ii) It may help establish the optimal duration of secondary VTE prevention with vitamin K antagonists, although the panel felt that this area needs further investigation when dealing with direct oral anticoagulants. (iv) The use of D-dimer in combination with the pre-test probability score can be used to safely rule out acute aortic syndromes in the emergency setting without further imaging tests.