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Validation, calibration, and specificity of quantitative D-dimer assays
1I Department of Medicine, University Hospital of Mannheim, Mannheim, Germany.
Seminars in Vascular Medicine
|November 23, 2005
Summary
D-dimer antigen assays utilize monoclonal antibodies to detect specific fibrin degradation products. Harmonizing these assays requires standards reflecting the diverse cross-linked fibrin compounds found in circulation.
Area of Science:
- Biochemistry
- Immunology
- Hematology
Background:
- D-dimer antigen assays rely on monoclonal antibodies targeting specific epitopes.
- These epitopes are generated through Factor XIII-induced cross-linking of fibrin gamma-chains.
- Plasmin degradation of cross-linked fibrin can also generate detectable epitopes for some antibodies.
Purpose of the Study:
- To describe the principles and challenges of D-dimer antigen assays.
- To highlight the nature of D-dimer antigen detected in clinical samples.
- To discuss requirements for assay harmonization.
Main Methods:
- Utilizing monoclonal antibodies specific for fibrin fragment D-dimer.
- Analyzing fibrin compounds in clinical plasma samples.
- Comparing various assay technologies including latex agglutination, light-scattering immunoassays, and ELISAs.
Main Results:
- D-dimer antigen assays detect various molecular weight fibrin compounds, including D-dimer fragments, higher-molecular-weight products, and X-oligomers.
- The majority of detected D-dimer antigen originates from circulating cross-linked soluble fibrin, not particulate clots.
- Differences in epitope reactivity among antibodies necessitate specific standard preparations for assay harmonization.
Conclusions:
- D-dimer antigen assays provide insights into fibrinolysis and thrombosis.
- Assay harmonization is crucial for accurate clinical interpretation and requires standards with diverse cross-linked fibrin compounds.
- Understanding the epitopes targeted by monoclonal antibodies is key to developing reliable D-dimer testing methods.