Fibrin Degradation Products (FDP)

Principle:
This assay detects the presence of circulating fragments of fibrin degradation products (FDPs) such as fibrinogen and soluble (non-cross linked) fibrin that are produced by the action of plasmin:

• Plasmin acts on these 2 substrates similarly, producing an initial cleavage product called fragment X.
• Plasmin then acts on fragment X, cleaving it into a transient fragment Y, and fragment D.
• Further cleavage of fragment Y, produces the terminal fibrin(ogen) degradation products, fragment D and E.
• Thus from one molecule of fibrinogen or soluble fibrin, 2 terminal FDP fragments D and one terminal fragment E is produced

Specimen:
There are assays for FDPs in both serum and plasma. Two MLs is preferred, but a minimum of 0.5 MLs is required

Expected Result(s) and/or Critical Values:
The mean normal serum FDP is 4.9 ± 2.8 µg/ml. (FDP levels are calculated by a factor of 2 µg/ml.) A 1:5 dilution corresponds with 10 µg/ml and 1:20 dilution corresponds with 40 µg/ml. Normal or slightly elevated samples will yield negative results in both dilutions.

Note: The FDP assay is used with the other coagulation tests to characterize bleeding disorders more completely. The results should never be interpreted alone, without evaluation of clinical signs and results of other coagulation tests. Any cause of pathologic intravascular coagulation (the most common of which is DIC), thrombosis, or severe internal hemorrhage (see below) can produce FDP's. In addition, any condition causing decreased clearance of FDPs by the liver and monocyte-macrophage system,

Controls:
Positive and negative controls are run with each batch of samples