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===Fibrin Degradation Products===
===Fibrin Degradation Products===
Fibrin Degradation Products
Definition
As a marker of fibrinolysis, fibrin degradation products (FDP), also known as fibrin split products (FSP), can be quantified by a test based on latex agglutination. The test uses antibodies to FSP which are measured using serial dilutions.
Technique
Serum is prepared in a series of dilutions (e.g., ½, ¼, 1/16). Latex particles onto which have been absorbed antibodies to FSP are added. If agglutination is seen, the test is positive at that dilution. The test is reported as the most dilute sample that agglutinates. The normal value is less than ¼ to ⅙.
Basic Science
Although well standardized and easy to perform, the FSP value may be difficult to interpret. The action of thrombin on fibrinogen is to cleave the protein and produce smaller compounds called fibrinopeptides, plus the fibrin monomer. This monomer polymerizes to form the fibrin gel. The gel is stabilized by the action of factor XIII, activated by thrombin.
The action of plasmin is to cleave both fibrinogen and fibrin. Its action is localized by its activation at the site of endothelial rupture, and the tight association of plasminogen and fibrin. The activity on fibrinogen forms small fragments, D and E. The action on fibrin polymer is to form larger fragments. These fragments are anticoagulants formed at the site of coagulation and serve to inhibit the action of thrombin on fibrinogen to form fibrin. Both are also measured by the technique described above.
Clinical Significance
Increased FDP is the laboratory expression of increased fibrinolysis. This may be part of a local problem of fibrin generation such as brain trauma, chronic bleeding, vascular thrombosis, prostate surgery, uterine disorders, or malignancy, or a systemic process, usually DIC. Patients with severe liver disease can have increased fibrinolysis on the basis of poor clearance of circulating plasminogen activators.
==References==
==References==