At a Glance
Why Get Tested?
To help rule out clotting (thrombotic) episodes and to help diagnose conditions related to thrombosis
When to Get Tested?
When you have symptoms of a thrombotic episode or a condition that causes acute and/or chronic inappropriate blood clot formation such as deep vein thrombosis (DVT), pulmonary embolism (PE), or disseminated intravascular coagulation (DIC) and to monitor the progress and treatment of DIC and other thrombotic conditions
A blood sample drawn from a vein in your arm
Test Preparation Needed?
The Test Sample
What is being tested?
D-dimer is one of the protein fragments that are produced when a blood clot dissolves in the body. When a blood vessel or tissue is injured and begins to bleed, a process called hemostasis is initiated by the body to create a blood clot to limit and eventually stop the bleeding. During this process, threads of a protein called fibrin are produced. These threads crosslink together to form a fibrin net, which, together with platelets, helps hold the forming blood clot in place at the site of the injury until it heals.
Once the area has had time to heal and the clot is no longer needed, the body uses an enzyme called plasmin to break the clot (thrombus) into small pieces so that it can be removed. The fragments of the disintegrating fibrin in the clot are called fibrin degradation products (FDP). One of the fibrin degradation products produced is D-dimer, which consists of variously sized pieces of crosslinked fibrin.
D-dimer is normally undetectable in the blood and is produced only after a clot has formed and is in the process of being broken down. When there is significant formation and breakdown of blood clots in the body, the D-dimer blood level can rise. The D-dimer test measures the level in the blood.
For a person who is at low or intermediate risk for thrombosis and/or thrombotic embolism, the strength of the D-dimer test is in its negative predictive value in a hospital emergency room setting. That means that a negative D-dimer test indicates that it is highly unlikely that a thrombus is present. However, a positive d-dimer test cannot predict whether or not a clot is present. It indicates that further testing is required.
There are several factors and conditions that are associated with inappropriate blood clot formation. One of the most common of these conditions is deep vein thrombosis (DVT), which involves clot formation in the deep veins of the body, most frequently in the legs. These clots may grow very large and block blood flow in the legs, causing swelling, pain, and tissue damage. It is possible for a piece of the clot to break off and travel to other parts of the body. This "embolus" can lodge in the lungs, causing a pulmonary embolus or embolism (PE).
While clots most commonly form in the veins of the legs, they may also form in other areas as well; for example, clots in coronary arteries are the cause of myocardial infarction (heart attacks). Clots may also form on the lining of the heart or its valves, particularly when the heart is beating irregularly (atrial fibrillation) or when the valves are damaged. Clots also may form in large arteries as a result of narrowing and damage from atherosclerosis. Pieces of such clots may also break off and cause an embolus that blocks an artery in another organ, such as the brain (causing a stroke) or the kidneys. Measurements of D-dimer can be used to help detect clots in any of these sites.
Measurements of D-dimer may also be ordered, along with other tests, to help diagnose disseminated intravascular coagulation (DIC). The D-dimer level will typically be very elevated in DIC. DIC is a complex, acute, sometimes life-threatening condition that can arise from a variety of situations including some surgical procedures, sepsis, poisonous snake bites, liver disease, and postpartum (after the delivery of a baby). With DIC, clotting factors are activated and then used up throughout the body. This creates numerous tiny blood clots and at the same time leaves the patient vulnerable to excessive bleeding. Steps are taken to support the affected person while the underlying condition resolves.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
Ask a Laboratory Scientist
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
Schreiber, D. (Updated 2010 June 10). Deep Venous Thrombosis and Thrombophlebitis. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/758140-overview through http://emedicine.medscape.com. Accessed August 2010.
Kamangar, N. and McDonnell, M. (Updated 2010 May 14). Pulmonary Embolism. eMedicine [On-line information]. Available online at http://emedicine.medscape.com/article/300901-overview through http://emedicine.medscape.com. Accessed August 2010.
Mayo Clinic Staff (2009 January 30) Thrombophlebitis. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/print/thrombophlebitis/DS00223/DSECTION=all&METHOD=print through http://www.mayoclinic.com. Accessed August 2010.
(© 2008). Focus on Blood Clots. Vascular Disease Foundation [On-line information]. PDF available for download at http://www.vdf.org/pdfs/VDF_FocusOnBloodClots.pdf through http://www.vdf.org. Accessed August 2010.
Lehman, C. et. al. (Updated 2010 January). Disseminated Intravascular Coagulation – DIC. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/DIC.html?client_ID=LTD#tabs=1 through http://www.arupconsult.com. Accessed August 2010.
Pagana, K. D. & Pagana, T. J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp 347-348.
Wu, A. (© 2006). Tietz Clinical Guide to Laboratory Tests, 4th Edition: Saunders Elsevier, St. Louis, MO. Pp 332-333.
(April 2009) Hui S, Mast A, D-dimer: A non-invasive triage test for patients with suspected DVT. Clinical Laboratory News, Volume 35, Number 4. Available online at http://www.aacc.org/publications/cln/2009/april/Pages/series0409.aspx through http://www.aacc.org. Accessed November 2010.
(August 2006) Bussey H. What is the D-dimer test? ClotCare Online Resources. Available online at http://www.clotcare.com/faq_ddimertest.aspx through http://www.clotcare.com. Accessed November 2010.
National Blood Clot Alliance. Blood Clot Signs, Symptoms and Risks. Available online at http://www.stoptheclot.org/learn_more/blood_clot_symptoms__dvt.html through http://www.stoptheclot.org. Accessed November 2010.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Tabers Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Disseminated Intravascular Coagulation Panel. AACC View Q&A [On-line information]. Available online at http://www.aacc.org/access/outcomes/18_disseminated_intravascular.stm through http://www.aacc.org/.
(2003 January). In Search of a Killer - Does D-dimer Help? American College of Emergency Physicians [On-line information]. Available online at http://www.acep.org/1,32394,0.html through http://www.acep.org.
(2001 July 17). Improving the Diagnosis of Pulmonary Embolism in the Emergency Department. Annals of Internal Medicine v135 (2) [On-line Journal]. Available online at http://www.annals.org/issues/v135n2/nts/200107170-00005.html through http://www.annals.org.
Strandness Jr., DE. Are Physical Findings Totally Useless In DVT/PE? Vascular Web, University of Washington School of Medicine [On-line information]. Available online at http://www.vascularweb.org/doc/54 through http://www.vascularweb.org.
Tan, J. (2000 December). Clinical Applications of the D-Dimer Assay in Deep Venous Thrombosis. San Bernardino County Medical Society Bulletin [On-line newsletter]. Available online at http://www.sbcms.org/southcalphysician/2000/nov-dec/art5.htm through http://www.sbcms.org.
Prazeres, G. Deep Vein Thrombosis - Part II. Internal Medicine MedStudents [On-line information]. Available online at http://www.medstudents.com.br/medint/medint5.htm through http://www.medstudents.com.br.
D-Dimer: Lifting the Veil of Confusion. Diagnostics today Online, Beckman Coulter [On-line information]. Available online at http://www.beckmancoulter.com/resourcecenter/diagtoday/articles/features/betterddimer.asp through http://www.beckmancoulter.com.
Began, T. (2002 October). Elisa D-Dimer: How Accurate For PE Diagnosis? PulmonaryReviews.com, vol 7 (10) [On-line information]. Available online at http://www.pulmonaryreviews.com/oct02/pr_oct02_ELISA.html through http://www.pulmonaryreviews.com.
Cortese Hassett, A. (2000 February). D-dimer Testing and Acute Venous Thromboembolism. Transfusion Medicine Update, The Institute for Transfusion Medicine [On-line information]. Available online at http://www.itxm.org/TMU2000/tmu2-2000.htm through http://www.itxm.org.
Titus, K. (2003 January). Identity crisis persistswhich D-dimer? CAP Today, In the News [On-line Journal]. Available online at http://www.cap.org/captoday/archive/2003/0103/DdimerCover.html through http://www.cap.org.
Cruickshank, M. (2001 January). Practical Treatment Guidelines, Suspected DVT. The Thrombosis Interest Group of Canada [On-line information]. Available online at http://www.tigc.org/eguidelines/suspdvt.htm through http://www.tigc.org.
Abumuhor, I. and Hope Kearns, E.(2002 April 26). Thrombotic Thrombocytopenic Purpura, Differential Diagnosis. The Virtual Health Care Team [On-line information]. Available online at http://www.vhct.org/case2300/diagnosis.shtml through http://www.vhct.org.
Venous Thromboembolism (VTE), Qualitative (Time Sensitive). ARUP's Guide to Clinical Laboratory Testing (CLT) [On-line information]. Available online at http://www.aruplab.com/guides/clt/tests/clt_250b.htm through http://www.aruplab.com.
Yen, S. (2001 March 27). D-Dimer For The Diagnosis Of Deep Vein Thrombosis. Internal Medicine Evidence Based Medicine Newsletter, Edition 8 [On-line Newsletter]. Available online at http://www.wshmc.org/wshcresidency/EBMNL/EBMNL032701.htm through http://www.wshmc.org.