Deep vein thrombosis laboratory tests: Difference between revisions
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=== Workup for Hypercoagulation === | === Workup for Hypercoagulation === | ||
*Activated [[protein C]] resistance | * It is not a routine practice to screen for hypercoagulibity workup among all patients with DVT. Screening for hypercoagulibity can be considered in specific situations, such as a young patient with no risk factors of [[thrombosis]], recurrent VTE, or a positive family history. A hypercoagulability workup should not be ordered among patients with known conditions that predispose to [[thrombosis]], such as recent [[surgery]], trauma, or [[cancer]]. | ||
*[[ | |||
*[[Protein C]] | * The workup for inherited hypercoagulability includes: | ||
*[[ | ** Activated [[protein C]] resistance | ||
*[[Antithrombin]] | ** [[Factor V]] Leiden mutation | ||
*[[Lupus anticoagulant]] | ** [[Protein C]] | ||
*[[Anticardiolipin antibodies]] | ** [[Protein S]], free and total. | ||
*Plasma [[homocysteine]] values | ** [[Antithrombin]] | ||
** [[Lupus anticoagulant]] | |||
** [[Anticardiolipin antibodies]] | |||
** Plasma [[homocysteine]] values | |||
==References== | ==References== | ||
Revision as of 15:01, 17 July 2014
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Overview
D-dimer is used in the diagnosis of deep vein thrombosis among patients with low or unlikely probability of venous thromboembolism.[1][2] While 500 ng/mL has long been the most commonly used cut off value for abnormal D-dimer concentration, recent studies suggest the use of an age adjusted cut-off concentration of D-dimer. The age adjusted cut-off value of D-dimer is 500 ng/mL for subjects whose age is less than 50 years, and the age multiplied by 10 for subjects older than 50 years.[3][4][5]
Laboratory Findings
D-Dimer
For a detailed discussion on D-dimer, please click here.
- D-dimer is a cross-linked fibrin degradation product and a marker of endogenous fibrinolysis. In the setting of ongoing thrombosis, D-dimer's concentration is elevated in the blood and thus makes it a screening tool to rule out DVT.
- D-dimer is the "test of choice" in patients who are considered to be "low risk" according to pre-test probability. 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. If D-dimer is elevated, then DVT should be confirmed with ultrasound.[6][7]
- The cut off value for abnormal D-dimer concentration is 500 ng/mL. Interpretation of D-dimer may be improved by using age adjusted levels:[3][4][5]
- Patients less than 50 years old: normal D-dimer is less than 500 µg/L
- In patients 50 years or older: normal D-dimer is adjusted to be age multiplied by 10
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".
D-dimer Elevation in Other Conditions
D-dimer can be elevated in following conditions, which should be kept in mind while assessing this biomarker in patients with suspected DVT:
- Malignancy
- Disseminated intravascular coagulation
- Elderly
- Infection
- Pregnancy
- Surgery/Trauma
- Inflammatory conditions
- Atrial fibrillation
- Stroke
Workup for Hypercoagulation
- It is not a routine practice to screen for hypercoagulibity workup among all patients with DVT. Screening for hypercoagulibity can be considered in specific situations, such as a young patient with no risk factors of thrombosis, recurrent VTE, or a positive family history. A hypercoagulability workup should not be ordered among patients with known conditions that predispose to thrombosis, such as recent surgery, trauma, or cancer.
- The workup for inherited hypercoagulability includes:
- Activated protein C resistance
- Factor V Leiden mutation
- Protein C
- Protein S, free and total.
- Antithrombin
- Lupus anticoagulant
- Anticardiolipin antibodies
- Plasma homocysteine values
References
- ↑ Wells PS, Owen C, Doucette S, Fergusson D, Tran H (2006). "Does this patient have deep vein thrombosis?". JAMA. 295 (2): 199–207. doi:10.1001/jama.295.2.199. PMID 16403932. Review in: Evid Based Med. 2006 Aug;11(4):119 Review in: ACP J Club. 2006 Jul-Aug;145(1):24
- ↑ Wells PS, Anderson DR, Rodger M, Stiell I, Dreyer JF, Barnes D; et al. (2001). "Excluding pulmonary embolism at the bedside without diagnostic imaging: management of patients with suspected pulmonary embolism presenting to the emergency department by using a simple clinical model and d-dimer". Ann Intern Med. 135 (2): 98–107. PMID 11453709.
- ↑ 3.0 3.1 Douma RA, Tan M, Schutgens RE, Bates SM, Perrier A, Legnani C; et al. (2012). "Using an age-dependent D-dimer cut-off value increases the number of older patients in whom deep vein thrombosis can be safely excluded". Haematologica. 97 (10): 1507–13. doi:10.3324/haematol.2011.060657. PMC 3487551. PMID 22511491.
- ↑ 4.0 4.1 Schouten HJ, Geersing GJ, Koek HL, Zuithoff NP, Janssen KJ, Douma RA; et al. (2013). "Diagnostic accuracy of conventional or age adjusted D-dimer cut-off values in older patients with suspected venous thromboembolism: systematic review and meta-analysis". BMJ. 346: f2492. doi:10.1136/bmj.f2492. PMC 3643284. PMID 23645857.
- ↑ 5.0 5.1 Righini M, Van Es J, Den Exter PL, Roy PM, Verschuren F, Ghuysen A; et al. (2014). "Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: the ADJUST-PE study". JAMA. 311 (11): 1117–24. doi:10.1001/jama.2014.2135. PMID 24643601.
- ↑ 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.