Focus on Diagnosis: A Primer on D-dimer

Cristyn N. Camet; Donald L. Yee

doi:10.1542/pir.32-1-31

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Cristyn N. Camet, MD*
Donald L. Yee, MD^†

^*Pediatric Resident.
^†Department of Pediatrics, Hematology-Oncology Section, Baylor College of Medicine, Houston, TX.

Author Disclosure
Drs Camet and Yee have disclosed no financial relationships relevant to this article. This commentary does not contain a discussion of an unapproved/investigative use of a commercial product/device.

Introduction

The D-dimer antigen is a degradation byproduct of the fibrinolytic process (Figure) and is commonly used as a biomarker in various clinical settings such as the evaluation of venous thromboembolism (VTE) and disseminated intravascular coagulation (DIC). Much more literature on and collective experience with use of the D-dimer assay exists for adult than pediatric patients. However, thrombotic complications are becoming increasingly recognized in infants and children, and reports on this assay's utility in a variety of other pediatric applications are increasing. This review examines the biochemical basis of D-dimer formation, issues raised by the varied testing methods used to measure D-dimer, and the scenarios in which this assay may provide information useful for medical management.

Figure.

Sequential process of fibrinogen cleavage, fibrin polymerization, cross-linking, and fibrinolysis that leads to degradation products containing the D-dimer antigen. This diagram is simplified by depicting only a single fibrin strand and degradation products of uniform composition. Adapted from Adam SS, Key NS, Greenberg CS. D-dimer antigen: current concepts and future prospects. Blood. 2009;113:2878–2887.

D-dimer Formation

D-dimer formation begins with cleavage of fibrinogen molecules by activated thrombin into fibrin monomers, which then polymerize. Thrombin activates fibrin-bound factor XIII to form factor XIIIa that, in turn, catalyzes formation of covalent bonds between D-domains of the polymerized fibrin. Finally, during fibrinolysis, plasminogen is activated to plasmin, which cleaves the fibrin polymers at specific locations and releases fibrin degradation products that vary in molecular weight and size but include moieties containing the exposed D-dimer antigen. Thus, D-dimer concentrations are increased under any conditions of increased fibrin formation, as with hemostasis, …