Advances in D-dimer testing: progress in harmonization of clinical assays and innovative detection methods

The D-dimer is a sensitive indicator of coagulation and fibrinolysis activation, especially valuable as a biomarker of intravascular thrombosis. Measurement of plasma D-dimer levels plays a crucial role in the diagnosis and monitoring of conditions such as deep vein thrombosis, pulmonary embolism, and disseminated intravascular coagulation. A variety of immunoassays, including enzyme-linked immunosorbent assays, latex-enhanced immunoturbidimetric assays, whole-blood aggregation analysis, and immunochromatography assays, are widely used in clinical settings to determine D-dimer levels. However, the results obtained from different D-dimer assays vary significantly. These assays exhibit intra-method coefficients of variation ranging from 6.4% to 17.7%, and the measurement discrepancies among different assays can be as high as 20-fold. The accuracy and reliability of D-dimer testing cannot be guaranteed due to the lack of an internationally endorsed reference measurement system (including reference materials and reference measurement procedures), which may lead to misdiagnosis and underdiagnosis, limiting its full clinical application. In this review, we present an in-depth analysis of clinical D-dimer testing, summarizing the existing challenges, the current state of metrology, and progress towards harmonization. We also review the latest advancements in D-dimer detection techniques, which include mass spectrometry and electrochemical and optical immunoassays. By comparing the basic principles, the definition of the measurand, and analytical performance of these methods, we provide an outlook on the potential improvements in D-dimer clinical testing.