Deep vein thrombosis laboratory tests: Difference between revisions
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===D-dimer=== | ===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]]. | 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]]. | ||
**Plasma D-dimer>500 ng/ml, PE present (Found to be 97% sensitive and 45% specific) | |||
**Plasma D-dimer<500 excludes PE (Have a high negative predictive value) | |||
====Specificity and Sensitivity==== | ====Specificity and Sensitivity==== | ||
Revision as of 17:11, 1 February 2013
Editor(s)-In-Chief: The APEX Trial Investigators, C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-In-Chief: Cafer Zorkun, M.D., Ph.D. [2] ; Kashish Goel, M.D.; Assistant Editor(s)-In-Chief: Justine Cadet
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Deep Vein Thrombosis Microchapters |
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Deep vein thrombosis laboratory tests On the Web |
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Risk calculators and risk factors for Deep vein thrombosis laboratory tests |
Overview
The lifetime incidence of DVT ranges from 2-5% in the general population. It accounts for a large number of ER visits and puts the patient at-risk for a 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 a detailed discussion on D-dimer, please visit D-dimer.
Laboratory Findings
Workup for hypercoagulation
- Activated protein C resistance
- factor V Leiden mutation
- Protein C
- protein S, free and total.
- Antithrombin
- Lupus anticoagulant
- Anticardiolipin antibodies
- Plasma homocysteine values
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.
- Plasma D-dimer>500 ng/ml, PE present (Found to be 97% sensitive and 45% specific)
- Plasma D-dimer<500 excludes PE (Have a high negative predictive value)
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". Thus, D-dimer has a high sensitivity (sNOUT) and low specificity (sPIN) for DVT. This means that D-dimer is a better test for "ruling out" DVT rather than "ruling in".
Elevated in Other Conditions
D-dimer can be elevated in following conditions, which should be kept in mind while assessing its validity in patients with suspected DVT:
- Malignancy
- Disseminated intravascular coagulation
- Elderly
- Infection
- Pregnancy
- Surgery/Trauma
- Inflammatory conditions
- Atrial fibrillation
- Stroke
Use in DVT Diagnosis
D-dimer is the "test of choice" in patients who are considered to be "low risk" according to pre-test probability. More information regarding the use of D-dimer in diagnosis of DVT can be found here. If D-dimer is elevated, then DVT should be confirmed with ultrasound.[1][2]
D-dimer is more useful if its negative rather than positive. It has a great negative predictive value in low to moderate risk patients of DVT.
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.