D-dimer for the diagnosis of pulmonary embolism: a call for sticking to evidence

Excerpt

Critically ill patients are at high risk of venous thromboembolism (VTE). However, the disease is often clinically silent, especially in these patients, and is not associated with any specific clinical sign or biologic marker. It is, therefore, particularly difficult to diagnose this condition in the ICU. D-dimers (DD) are cross-linked fibrin derivatives that are produced upon fibrin degradation by plasmin. The DD concentration rises in various conditions in which coagulation and fibrinolysis are activated, e.g. in patients with VTE, but also in patients with cancer, myocardial infarction, infectious or inflammatory diseases, pregnancy and in the postoperative period. Practically, patients with acute VTE are very likely to present with an elevated DD level, corresponding to a very high sensitivity to VTE, which in turn results in a high negative predictive value. On the other hand, as DD rise in various pathologic conditions [1], the proportion of patients with increased DD may be substantial in patients without VTE: the specificity (proportion of patients with negative D-dimer test among those without VTE) of DD testing is low, resulting in a poor positive predictive value (PPV, proportion of patients with VTE among those with positive D-dimer tests). …