From: Elizabeth M. Van Cott, M.D., and Michael Laposata, M.D., Ph.D., “Coagulation.” In: Jacobs DS et al, ed. The Laboratory Test Handbook, 5th Edition. Lexi-Comp, Cleveland, 2001; 327-358.
Related Information
Disseminated Intravascular Coagulation Screen
Hypercoagulation Panel
Synonyms D-Dimers; FBP; FDP; Fibrin Breakdown Products; Fibrin Split Products; FSP
Applies to Fibrinolysis; Plasmin; Thrombin; Thrombolysis
Abstract Fibrinolysis is mediated by plasmin, which degrades fibrin clots into D-dimers and fibrin degradation products (FDP). Plasmin can also degrade intact fibrinogen, generating fibrinogen degradation products (FDP) that are detected in FDP assays.
Specimen Plasma (some FDP assays require serum; the SimpliRed® D-dimer assay uses whole blood)
Container One blue top (citrate) tube (some FDP serum assays require special tubes that contain thrombin to clot the blood, and a fibrinolysis inhibitor to prevent FDP formation in the test tube)
Collection Routine venipuncture. If multiple tests are being drawn, draw blue top tubes after any red top tubes but before any lavender top (EDTA), green top (heparin), or gray top (oxalate/fluoride) tubes. Immediately invert tube gently at least 4 times to mix. Tubes must be appropriately filled. Deliver tubes immediately to the laboratory.
Storage Instructions Separate plasma from cells as soon as possible. Store plasma at room temperature for up to 8 hours, on ice for up to 24 hours, or store frozen. (Serum: Once serum is obtained, it may be refrigerated for up to 1 week, or it may be stored frozen.)
Causes for Rejection Clotted specimens are unsuitable for plasma-based tests.
Turnaround Time Less than 1 day (latex agglutination methods take less than 1 hour; standard ELISA methods take 5 hours; rapid ELISA methods have been developed)
Reference Interval D-dimer: approximately <0.5 microg/mL; FDP: approximately <5 microg/mL
Use D-dimers or FDP are part of a panel of tests required for diagnosing DIC. In DIC, both thrombin and plasmin are generated, causing an elevation in D-dimers and FDP. See Disseminated Intravascular Coagulation Screen.
D-dimers assist with the diagnosis of deep venous thrombosis (DVT) and pulmonary embolism (PE), but only if a very sensitive method is used. If the test is positive in a patient suspected to have DVT or PE, clinicians proceed with further diagnostic tests for DVT or PE. If the test is negative, depending on the clinical situation and the sensitivity of the D-dimer assay, DVT or PE is considered unlikely and further diagnostic tests for DVT or PE might not be pursued.1,2
Monitoring thrombolytic therapy is not routinely required. However, if monitoring is desired, D-dimers or FDP are one of several tests that can be performed to confirm that thrombolysis (fibrinolysis) is occurring. D-dimers and FDP should become increased with thrombolytic therapy.
Limitations D-dimers and FDP can become elevated whenever the coagulation and fibrinolytic systems are activated. This occurs in a variety of conditions, and therefore the tests are not specific for any one diagnosis.
Manual latex agglutination and certain other methods are not sufficiently sensitive to exclude the diagnosis of DVT or PE when the test result is negative. Even with the most sensitive methods (eg, ELISA assays), a patient with PE or DVT may test negative for D-dimers.
High rheumatoid factor (RF) levels may cause false-positive results with some assays.
Methodology Assays are semiquantitative or quantitative immunoassays.
Latex agglutination: Patient plasma is mixed with latex particles which are coated with monoclonal anti-FDP antibodies.3 If FDP are present in the patient plasma, the latex particles agglutinate as FDP bind to the antibodies on the particles. These large agglutinated clumps are detected visually by the technologist. Various dilutions of patient plasma can be tested to provide an estimation of the FDP titer (semiquantitative result). Latex agglutination assays are also available for D-dimers. Automated, quantitative versions of this assay are commercially available for D-dimers (MDA® D-dimer, Organon Teknika; STA Liatest®, Diagnostica Stago), in which the agglutination is detected turbidimetrically by a coagulation analyzer rather than visually by a technologist.4,5
Enzyme-linked immunosorbent (ELISA) assays: Quantitative ELISA assays are available for FDP, D-dimers, or fibrinogen degradation products. An automated, rapid ELISA assay for D-dimers is available (VIDAS®, bioMerieux Inc).1,2,6
Other methods: SimpliRed® D-dimer (American Diagnostica) is a semiquantitative red blood cell agglutination assay that can be performed on whole blood. Other methods have been developed that are not yet available in the United States.
Additional Information A D-dimer is a specific FDP that is formed only by plasmin degradation of fibrin, and not by plasmin degradation of intact fibrinogen. Thus, the presence of D-dimers indicates that fibrin has been formed and degraded. In contrast, a positive FDP assay indicates that fibrin and/or fibrinogen is being degraded by plasmin, because the FDP assay detects fibrin degradation products, including D-dimers, and fibrinogen degradation products. D-dimers and FDP can be positive with DIC or thrombosis, including DVT, PE and myocardial infarction. They also may be positive in liver disease due to decreased hepatic clearance. They can become elevated postoperatively, and with significant bleeding, hemodialysis, eclampsia, sickle cell crisis, and other conditions. Cancer patients often have positive D-dimers and FDP, usually representing low-grade, chronic DIC. D-dimers and FDP mildly increase in pregnancy.
In the past, FDP had to be performed on serum samples, because the polyspecific antibodies cross-react with fibrinogen in plasma. Fibrinogen is not present in serum because it has been converted into fibrin clot, centrifuged, and discarded. Currently, monoclonal antibodies specific for FDP, without cross-reactivity against fibrinogen, allow the test to be performed in plasma. There is some evidence that the older, serum-based assays are not as reliable as the newer, plasma-based assays, because serum-based FDP may give low values due to trapping of FDP in the clot, or high values due to generation of FDP during clot formation.7
Footnotes
1. van der Graaf F, van den Borne H, van der Kolk M, et al, “Exclusion of Deep Venous Thrombosis With D-Dimer testing. Comparison of 13 D-Dimer Methods in 99 Outpatients Suspected of Deep Venous Thrombosis Using Venography as Reference Standard,”Thromb Haemost, 2000, 83(2):191-8.
2. Perrier A, Desmarais S, Miron MJ, et al, “Noninvasive Diagnosis of Venous Thromboembolism in Outpatients,”Lancet, 1999, 353(9148):190-5.
3. Mirshahi M, Soria J, Soria C, et al, “A Latex Immunoassay of Fibrin/Fibrinogen Degradation Products in Plasma Using a Monoclonal Antibody,”Thromb Res, 1986, 44(6):715-28.
4. Escoffre-Barbe M, Oger E, Leroyer C, et al, “Evaluation of a New Rapid D-Dimer Assay for Clinically Suspected Deep Venous Thrombosis (Liatest® D-Dimer),”Am J Clin Pathol, 1998, 109(6):748-53.
5. Bates SM, Grand’Maison A, Johnston M, et al, “A Latex D-Dimer Reliably Excludes Venous Thromboembolism,”Thromb Haemost, 1999, 82(Suppl):258.
6. Pittet JL, de Moerloose P, Reber G, et al, “VIDAS® D-Dimer: Fast Quantitative ELISA for Measuring D-Dimer in Plasma,”Clin Chem, 1996, 42(3):410-15.
7. Gaffney PJ and Perry MJ, “Unreliability of Current Serum Fibrin Degradation Product (FDP) Assays,”Thromb Haemost, 1985, 53(3):301-302.
References
Freyburger G, Trillaud H, and Labrouche S, “D-Dimer Strategy in Thrombosis Exclusion. A Gold Standard Study in 100 Patients Suspected of Deep Venous Thrombosis or Pulmonary Embolism: 8 DD Methods Compared,”Thromb Haemost, 1998, 79(1):32-7.
