Review of D‐dimer testing: Good, Bad, and Ugly

D‐dimer assays are commonly used in clinical practice to exclude a diagnosis of deep vein thrombosis or pulmonary embolism. More recently, they have been also been used to guide patients with unprovoked venous thromboembolism (VTE) when faced with the decision to continue or stop anticoagulation after initial treatment is complete. D‐dimer assays vary widely with respect to the antibody used, method of capture, instrumentation required, and calibration standard. These differences have an important influence on the operating characteristics of the assays. Consequently, the evidence available in the literature for one assay cannot simply be extrapolated to another. In this review, we will outline the general properties of D‐dimer assays, discuss the concept of raising the D‐dimer threshold used in diagnosis of VTE according to pretest probability and age, and provide clinical perspective on the role of D‐dimer testing in the diagnosis and prognosis of VTE.