Fibrinogen degradation products (FDPs) and d-Dimer

What Sample is needed for Fibrinogen Degradation Products (FDPs)?

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, citrated plasma is stable for 8 hours at room temperature.

What is the purpose of the test for Fibrinogen Degradation Products (FDPs)?

1. This test establishes a DIC diagnosis (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.

What Precautions will you take for Fibrinogen Degradation Products (FDPs)?

1. Keep in mind that menstruation may be associated with increased FDP value.
2. Remember that drugs like barbiturates, streptokinase, urokinase, and heparin may increase their 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.
6. Some of the drugs may affect and increase the level of FDPs like:
   1. When heparin was given to treat the blood clots.
   2. When streptokinase is given in patients with coronary thrombosis.
   3. Barbiturates may increase the FDP level.
   4. Treatment by the urokinase to dissolve the clot.
   5. Drugs affecting the FDP level:

How will you define fibrinogen degradation products (FDPs)?

1. Fibrinogen Degradation Products (FDPs) are the substances left behind when a clot dissolves in the blood.
2. Fibrinogen Degradation Products (FDPs) are the fragments released following plasmin-mediated degradation of fibrinogen or fibrin.
3. d-dimer is a specific fragment formed after the degradation of the cross-linked fibrin.
4. FDPs are raised mostly >40 µg/mL in 85% to 100% of the patients with DIC.
5. FDPs are also raised in thromboembolism, acute myocardial infarction, transplant rejection, and surgery.

How will you discuss the pathophysiology of Fibrinogen/Fibrin degradation products (FDPs and d-dimer)?

1. Normal homeostasis is a balanced interaction of the vascular endothelium,  platelets, and biochemical systems.
2. Measurement of FDPs provides a direct indication of the activity of the fibrinolytic system.
3. The Fibrinolytic system is important in balancing clot formation and clot dissolution.

Fibrinogen Degradation Products (FDPs): Normal blood homeostasis

4. FDPs are generated when inappropriate clotting is seen in disseminated intravascular coagulopathy (DIC).

FDPs and d-Dimer formation and consequences

What is a summary of fibrinogen degradation products (FDPs)?

1. Plasmin actually leads to fibrinogen/fibrin degradation products (FDPs).
2. Plasmin has a strong affinity for fibrin but can not differentiate between fibrinogen and fibrin.

What is the trigger for this excessive intravascular coagulopathy?

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.
   1. All the above factors lead to the release of procoagulants and give rise to platelet aggregation.
   2.  Gram-negative and meningococcal septicemia, septic abortion, and viral diseases lead to endothelial injury and cause intravascular clot formation.

FDPs and d-Dimer formation.

Fibrinogen degradation products (FDP) and d-Dimer facts:

1. When the body tries to dissolve blood clots, these are polypeptide fragments generated by the enzymes (plasmin).
2. These fibrinogen degradation products are named X, Y, D, and E and are collectively called fibrinogen degradation products (FDP) and d-dimer.

d-dimer

1. It is more specific for the measurement of fibrinogen degradation. At the same time, normal plasma is negative for d-dimer.
2. These FDPs have anticoagulant action and inhibit clotting.

Role of Plasmin and d-Dimer

Fibrinogen degradation product types and action

3. FDP is the substance that remains in the blood after the blood clot is dissolved.
   1. The FDPs have an anticoagulant action and inhibit clotting when in excess.
   2. FDPs and d-Dimer correlate with each other and are evidence for DIC or another intravascular thrombosis.
4. FDPs and d-Dimer assess both thrombin and plasmin activity.
5. The d-Dimer assay provides a highly specific measurement of fibrin degradation that occurs.

 Disseminated intravascular coagulopathy (DIC):

Definition of DIC:

1. DIC is an acquired coagulation disorder.
2. Excess systemic activation of the coagulation system leads to widespread microthrombi in circulation.
3. End result is depletion of the platelets and coagulation factors, leading to bleeding.
4. Activation of the thrombin leads to thrombosis of small and medium size blood vessels.

Signs and symptoms of DIC:

1. There may be 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.

Diagnosis of DIC:

1. Platelet count is decreased.
2. Fibrinogen level is decreased.
3. The protamine sulfate test is positive.
4. Factor V and XIII are decreased.
5. d-Dimer is positive (FDPs are positive).
6. Prothrombin time is increased.
7. APTT is increased.

Normal FDPs and d-Dimer

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.
  • The 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 FDPs are done, they are more specific for the diagnosis of DIC.

Increased FDPs 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.

What are the conditions where FDPs are increased in urine?

1. It is seen in kidney diseases.
2. Urinary tract infection.
3. Proliferative glomerulonephritis.
4. Rejection of renal transplant.

Decreased FDP value seen in:

• Anticoagulant therapy.

The critical value of FDP is above  >40 µg/mL or 40 mg/L.

Questions and answers: