D-dimer assay guidelines: value of objective testing for VTE in the emergency setting

Venous thromboembolism (VTE) is a dangerous and potentially fatal medical condition accounting for approximately 25,000 deaths annually in the UK alone. It cannot be diagnosed solely on the basis of clinical presentation due to the lack of sensitivity and specificity of signs and symptoms.The high-sensitivity, automated D-dimer laboratory assay plays a critical role in the diagnostic algorithm (Fig 1) that clinicians use for the exclusion of VTE in the emergency situations.

            Currently, there is still no formal international standard, resulting in various assays with different cut-offs and clinical performances. Efforts to standardise D-dimer results have not proved successful because the D-dimer analyte – a marker of endogenous fibrinolysis – is not consistent across the different assays.

            To help clinicians and laboratories improve diagnosis strategies and patient care, several internationally respected organisations, such as the Clinical and Laboratory Standards Institute (CLSI), have published more stringent guidelines. A key aspect focuses on the need for objective laboratory testing as clinical assessment alone is often unreliable. Emergency clinicians need to have a robust D-dimer result to enable them to implement the appropriate medical care. It is also important to avoid unnecessary anticoagulant therapy, which carries its own risks.