Deep vein thrombosis laboratory tests
Editors-in-Chief: C. Michael Gibson, M.S., M.D. Associate Editor-In-Chief: Ujjwal Rastogi, MBBS[1]; Kashish Goel, M.D.
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Overview
The lifetime incidence of DVT ranges from 2-5% in general population. It accounts for a large number of ER visits and puts the patient at-risk for life-threatening pulmonary embolism. The use of D-dimer after assessment of pre-test probability has been widely validated now and has led to a significant reduction in unnecessary procedures in the ER and hospital settings. This chapter will review the role of D-dimer in diagnosis of DVT. For detailed discussion on D-dimer, please visit
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D-dimer
D-dmer is a cross-linked fibrin degradation product and a marker of endogenous fibrinolysis. In the setting of ongoing thrombosis, its levels should be elevated in the blood that makes it an excellent screening tool to rule out DVT.
Specificity and Sensitivity
A large number of D-dimer assays are available and may vary in-between hospitals. In a meta-analysis of 217 studies involving DVT patients, the sensitivities of the D-dimer enzyme-linked immunofluorescence assay (ELFA) (96%), micro plate enzyme-linked immunosorbent assay (94%), and latex quantitative assay (93%; PE 95%) were superior to the whole-blood D-dimer assay (83%), and latex qualitative assay (69%). Because of this, ELISA assays are termed as "highly sensitive" and whole blood D-dimer assays is "moderately sensitive".
Elevated in other conditions
Use in DVT diagnosis
In a low-probability situation, current practice is to commence investigations by testing for D-dimer levels. This cross-linked fibrin degradation product is an indication that thrombosis is occurring, and that the blood clot is being dissolved by plasmin. A low D-dimer level should prompt other possible diagnoses (such as a ruptured Baker's cyst, if the patient is at sufficiently low clinical probability of DVT.[1][2]
It should be noted that latex D-dimer assays are insensitive and have no role in screening for deep vein thrombosis.
References
- ↑ Wells PS, Anderson DR, Rodger M; et al. (2003). "Evaluation of D-dimer in the diagnosis of suspected deep-vein thrombosis". N. Engl. J. Med. 349 (13): 1227–35. doi:10.1056/NEJMoa023153. PMID 14507948.
- ↑ Bates SM, Kearon C, Crowther M; et al. (2003). "A diagnostic strategy involving a quantitative latex D-dimer assay reliably excludes deep venous thrombosis". Ann. Intern. Med. 138 (10): 787–94. PMID 12755550.