SimpliRED D-dimer

The D-dimer assay you can trust

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3B6

BBI SimpliRED D-dimer uses a monoclonal antibody (MAB) coded DD 3B6/22 or 3B6 for short. This antibody is highly specific for D-dimer.

The epitope recognised by 3B6 resides between amino acids 86 & 302 in the gamma chain of the D domain chains of fibrinogen (i.e. Fragment D).

This epitope is masked in soluble non-cross linked or non-degraded fibrin but becomes expressed after cross-linked fibrin has been cleaved by plasmin.1

Expression of this region, which is specific to fibrin derivatives, can be utilized to differentiate between fibrin and fibrinogen breakdown products. The smallest and best characterized of the fibrin breakdown products is D-dimer, comprising two cross-linked D domains.2

3B6 demonstrates reactivity with D-dimer, & other cross-linked fibrin degradation products containing D-dimer, but no reactivity with Fragment D or E.

Additionally no cross reaction was found with purified intact fibrinogen or fibrinogen degradation products.3,4

Commercially available D-dimer kits differ in reactivity toward D-dimer. Standardization of D-dimer assays has been under review of the Fibrinogen and DIC subcommittees of the International Society on Thrombosis and Haemostasis (ISTH) for several years, involving three international surveys (1992-1995). The reactivity of different commercial kits to various standards is widely variable and this implies that an international D-dimer standard may not be feasible. The FACT (Fibrin Assay Comparison Trial) 5, sponsored by the ISTH sub-committee on fibrinolysis, was designed to generate initial data for the development of reference calibrators and standard preparations. All D-dimer assay manufacturers were invited to participate and all accepted providing calibrators and assay material for analysis. The study outcomes highlighted that:

• The predominant reason for discrepancies between D-dimer assays is related to differences in antibody specificity, especially concerning the preference for high or low molecular weight fibrin derivatives.
• Differences concerning analyte reactivity will become more evident in samples containing an unusual composition of fibrin derivatives. In samples from patients with hyperfibrinolytic conditions (i.e. pregnancy, DIC), or treatment with profibrinolytic drugs, D-dimer assays with a preference for high molecular weight fibrin compounds will show lower levels of D-dimer antigen than assays which detect the D-dimer epitope irrespective of the molecular size of the D-dimer containing molecule.
• Assays displaying cross-reactivity with non-cross linked fibrinogen and fibrin derivatives will show erroneously high levels of antigen in such conditions.
• Certain assays showed greater than 30% cross-reactivity with degradation products of fibrinogen.
• Others showed preference for high molecular weight D-dimer and little reactivity with fragment D-dimer.
• Assays using DD3B6/22 were identified as the most specific for D-dimer, irrespective of molecular weight of the D-dimer containing structure.

• 1.  Devine D.V., Greenberg C.S. Monoclonal Antibody to Fibrin D-Dimer DD-3B6 Recognizes an Epitope on the g- Chain of Fragment D. American Journal of Clinical Pathology, Vol.89:5; 663-666.1988
• 2.  Hillyard C.J., Blake A.S., et al. A Latex Agglutination Assay for D Dimer: Evaluation and Application to the Diagnosis of Thrombotic Disease. Clinical Chemistry, 33, No. 10, 1987
• 3.  Rylatt D.B., Blake A.S., et al. An Immunoassay for Human D-dimer using Monoclonal Antibodies. Thrombosis Research 31; 767-778. 1983
• 4.  Bundessen et al. Monoclonal antibodies with Specificity for Crosslinked Fibrin Derivatives and Assay for Said Derivatives. United States Patent, No: 4,758,524., Jul. 19, 1988
• 5.  Dempfle CE et al. The Fibrin Assay Comparison Trial (FACT). Evaluation of 23 Quantitative D-dimer Assays as Basis for the Development of D-dimer Calibrators. Thromb Haemost 2001; 85:671-8

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