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Coagulation

Coagulation laboratory tests

D-dimer / dimerized plasmin fragment D


Reviewer: Jeremy Parsons, M.D. (see Reviewers page)
Revised: 20 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.

General
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● Marker of ongoing procoagulant activity
● Fibrin degradation products (fibrin split products) that are formed only by plasmin degradation of fibrin, not by plasmin degradation of intact fibrinogen, thus indicating that fibrin has been formed
● D-regions of fibrinogen are crosslinked by factor XIII after the fibrin clot is formed
● Plasmin cannot cleave the bond between the D-regions, so dimers are also found when a clot is broken down
● Normal plasma level is probably due to physiologic clotting activity

Specimen:
● Usually plasma with citrate anticoagulant
● Values < 0.5 mg/L with quantitative ELISA assays have good negative predictive value for thromboembolic disorders
● Other values are not predictive (Arch Pathol Lab Med 2004;128:519)

Suggested guidelines for D-dimer testing to rule out pulmonary emboli in patients with low clinical suspicion (if moderate or high clinical suspicion, should do imaging studies):
● Age < 70 years, and no unexplained hypoxemia, unilateral leg swelling, recent surgery, hemoptysis, pregnancy or prolonged duration of symptoms (Acad Emerg Med 2005;12:20)
● Elevated levels are sensitive but not specific for DIC
● Elevated levels after completion of oral anticoagulation are associated with venous thromboemboli

LIA assay:
● Mix patient plasma with latex particles coated with monoclonal anti-D-dimers or fibrin degradation product antibodies
● Detect agglutination with coagulation analyzer and semiquantitate with dilutions
● Although this is called a Latex ImmunoAssay, it differs from the qualitative latex agglutination assay that is NOT predictive of pulmonary emboli

ELISA method:
● Also available

False positives:
● Recent surgery
● HIV+ Castlemanís disease due to interference from monoclonal gammopathy (Arch Pathol Lab Med 2004;128:328)
● High rheumatoid factor
● Liver disease
● Cancer patients
● Pregnancy

Note:
● Some platforms use fibrinogen equivalent units, which are 50% the numerical value of d-dimer units

Clinical images
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Fibrin split products/ D-dimer

Additional references
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Antovic, J.P. and Egberg, N. (2010). Laboratory investigations. In M. Blomback and J.P. Antovic (Eds.), Essential Guide to Blood Coagulation (pp.11-33). Oxford, UK: Wiley-Blackwell.

End of Coagulation > Coagulation laboratory tests > D-dimer / dimerized plasmin fragment D


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