Fibrinogen Degradation products (FDP) or Fibrin split products (FSP), and d-Dimer

Sample

1. It is done in the serum.
2. Collect 2 ml blood in a test tube containing Thrombin,  soybean, and Trypsin inhibitor.
3. Allow to clot at 37 °C for 30 min.
4. OR Collect blood with 1:20 dilution (ESR solution 0.2 ml and 1.8 ml blood).
5. For d-Dimer plasma (citrate) is stable for 8 hours at room temperature.

Purpose of the test (Indications)

1. This test is done to establish the diagnosis of DIC (Disseminated intravascular coagulopathy).
2. Thromboembolic disorders like pulmonary embolism.
3. This is a screening test for DVT (Deep vein thrombosis).
4. It can be used to determine the duration of anticoagulation treatment of DVT.

Precautions

1. Keep in mind that menstruation may be associated with increased FDP value.
2. Keep in mind that drugs like barbiturates, streptokinase, urokinase, and heparin may increase the value.
3. Some drugs like warfarin and other oral anticoagulants decrease the value.
4. Avoid the excessive agitation of the blood.
5. Avoid prolonged use of a tourniquet.

Pathophysiology

1. The normal homeostasis is a balanced interaction of the vascular endothelium,  platelets, and four biochemical systems.

2. FDPs generates when there is inappropriate clotting seen in disseminated intravascular coagulopathy (DIC).

3. The trigger for this excessive intravascular coagulopathy may be:
   1. Severe trauma.
   2. Amniotic fluid embolism.
   3. Premature separation of the placenta.
   4. Mucinous Adenocarcinoma.
   5.  Liver diseases.
   6. Acute myelocytic leukemia.
   7. Falciparum malaria.
   8. Snake Bites.
4. All the above factors lead to the release of procoagulants and give rise to platelets aggregation.
   1.  Gram-negative and meningococcal septicemia, septic abortion, and viral diseases lead to endothelial injury and cause intravascular clot formation.

5. Fibrinogen degrades products (FDP) are polypeptide fragments that are generated by the enzymes when the body tries to dissolve blood clots.
   1. These fibrinogen degradation products are named X, Y, D, and E, and collectively called fibrinogen degradation products (FDP).
   2. These FDPs have anticoagulant action.

6. FDP is the substances that remain in the blood after the blood clot is dissolved.
   1. Fibrin is split by Plasmin and form fibrin degradation products, and d-Dimer.
   2. The FDP has an anticoagulant action and inhibits clotting when these are present in excess.
   3. FDP and d-Dimer correlate with each other and are evidence for DIC or another intravascular thrombosis.
7. FDP and d-Dimer assess both thrombin and plasmin activity.

8. The d-Dimer assay provides a highly specific measurement of fibrin degradation that occurs.
9. Normal plasma has no detectable d-Dimer.

Symptoms of DIC:

1. There may Nausea and vomiting.
2. The patient may have bleeding from the gums.
3. There is severe muscular pain.
4. There may be abdominal pain.
5. The patient will have reduced urinary output (oliguria) and hematuria.
6. There is dyspnea.
7. Ultimately shock and confusion.

Drugs affecting the FDP level:

1. Some of the drugs may affect and increase the level of FDP in the like:
2. When heparin was given to treat the blood clots.
3. When streptokinase is given in patients with coronary thrombosis.
4. Barbiturates may increase the FDP level.
5. Treatment by the urokinase to dissolve the clot.

Normal

Source 1

• FDP = <10  µg/mL
• To convert to SI unit x 1.0 = <10 mg/L

Source 4

• FDP = Negative at 1:4 Dil.
  • Quantitative value is <10 µg /ml or <10 mg/L.
• d-Dimer is more specific than FDP.
  • Negative = No d-Dimer fragments are found in plasma.
  • <0.25 mg/L (or <0.4 µg/mL).

Source 2

• Negative, no d-dimer fragments are found.
  • <250 ng/mL  (<250 µg/L)
• When both test d-Dimer and FDP are done are more specific for the diagnosis of DIC.

Increased FDP or d-Dimer level is seen in:

1. Pregnancy ( abruptio placentae, Eclampsia, retained dead fetus, and sepsis ).
2. Myocardial infarction.
3. Heart or vascular surgery.
4. Thrombosis.
5. Pulmonary embolism.
6. Thrombolytic or defibrination therapy.
7. Primary and secondary fibrinolysis.
8. in the case of DIC.
9. Venous thrombosis (Deep vein thrombosis, DVT).
10. Carcinomas.
11. Liver disease.
12. Surgery.
13. Allograft rejection.
14. Hematoma.
15. Sickle cell anemia.
16. Massive trauma.

Decreased FDP value seen in:

• Anticoagulant therapy.

Critical Value of FDP is above  >40  µg/mL or 40 mg/L

 

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