🩸 FDP (Fibrin/Fibrinogen Degradation Products) — Complete Guide

🩸 FDP (Fibrin/Fibrinogen Degradation Products) — Complete Guide

A key biomarker reflecting fibrin formation, fibrinolysis, and fibrinogen degradation, widely used in evaluating DIC, hyperfibrinolysis, and thrombotic/bleeding disorders.

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1. What Are FDPs?

FDPs (Fibrin/Fibrinogen Degradation Products) are fragments produced when fibrinogen or fibrin undergoes degradation by plasmin.

• Fibrinogen → FDPs
• Cross-linked fibrin → FDPs + D-dimer

Therefore, FDP reflects two pathways:

1. Fibrin formation + breakdown
2. Fibrinogen degradation (primary fibrinolysis)

Unlike D-dimer, which is specific to cross-linked fibrin, FDPs indicate a broader fibrinolytic and coagulopathic activity.

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2. Clinical Indications

✔ 1) Diagnosis & monitoring of DIC (Disseminated Intravascular Coagulation)

Hypercoagulation + fibrinolysis → marked elevation of FDP.

✔ 2) Evaluation of fibrinolytic activity

Particularly useful in primary fibrinolysis, where fibrinogen degradation predominates.

✔ 3) Adjunct marker in thrombotic diseases

FDP elevations may accompany DVT, PE, thrombosis, but
→ D-dimer remains the preferred “rule-out” test.

✔ 4) Coagulopathy associated with systemic illness

• Sepsis
• Severe liver dysfunction
• SIRS
• Trauma

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3. Test Method: Immunoturbidimetry

Most laboratories use latex-enhanced immunoturbidimetric assays.

🔬 Principle

• Latex particles coated with anti-FDP antibodies are mixed with plasma.
• FDPs bind → agglutination occurs.
• Increasing turbidity is optically measured.
• Higher turbidity = higher FDP concentration

Advantages

• Rapid, automated
• Suitable for ER, ICU settings
• Good analytical reproducibility

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4. Specimen Requirements

• Sample: 3.2% sodium citrate plasma (light blue top)
• Mix immediately after collection
• Use platelet-poor plasma after centrifugation
• Interferences:
  • Hemolysis
  • Icterus
  • Lipemia (can artificially increase turbidity)

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5. Reference Range

Varies by institution and units, but generally:

• FDP < 5.0 μg/mL

⚠ Units differ significantly (μg/mL, mg/L, μg/L).
Always confirm with local laboratory reference values.

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6. Clinical Significance

🟥 FDP Elevated

1) DIC (Disseminated Intravascular Coagulation)

• Excess coagulation + plasmin activation
• FDP and D-dimer both markedly increased

2) Primary fibrinolysis

• Fibrinogen breakdown without clot formation
• FDP ↑, D-dimer normal or mildly ↑
  → FDP/D-dimer comparison is diagnostically useful

3) Liver disease

Coagulation factor deficiency + enhanced fibrinolysis.

4) Major trauma, surgery, burns

Tissue destruction → increased fibrin turnover.

5) Obstetric complications

Abruptio placentae, amniotic fluid embolism, postpartum hemorrhage.

6) Advanced malignancy

Tumor-associated coagulopathy → FDP elevation.

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🟦 FDP Decreased or Normal

• Not clinically significant.
• Reflects absence of active fibrinolysis or fibrinogen breakdown.
• For thrombus exclusion, D-dimer is much more sensitive.

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7. FDP vs D-dimer — Key Comparison

Feature	FDP	D-dimer
Source	Fibrinogen + fibrin degradation	Cross-linked fibrin only
Specificity	Lower	Higher
Primary fibrinolysis	Markedly ↑	Normal or mild ↑
DIC	↑	↑
VTE rule-out	❌ Not recommended	✔ Standard test

Summary

• FDP → broad overview of coagulation & fibrinolysis
• D-dimer → specific for thrombus formation/breakdown

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8. Interpretation Precautions

✔ 1) FDP has low specificity

Elevated in inflammation, infection, surgery, liver disease.

✔ 2) Key marker for primary fibrinolysis

FDP↑ + D-dimer normal → consider primary fibrinolysis.

✔ 3) Pre-analytical errors matter

• Hemolysis → false results
• Lipemia → interferes with turbidity-based assays

✔ 4) Watch unit variability

Must interpret according to the report’s unit of measurement.

✔ 5) DIC evaluation requires a full panel

Interpret FDP with:

• Platelet count
• PT/INR
• aPTT
• Fibrinogen
• D-dimer

🩸 D-dimer Test: Complete Medical Review – MedLab Insight

Heparin-Induced Thrombocytopenia (HIT) (26)

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9. References

1. Rodak BF. Hematology: Clinical Principles and Applications.
2. Dacie and Lewis. Practical Haematology.
3. Levi M. Disseminated Intravascular Coagulation. N Engl J Med.
4. CLSI—Coagulation Standards.
5. Lippi G. Fibrin Degradation Products in Hemostasis. Semin Thromb Hemost.

https://pubmed.ncbi.nlm.nih.gov/11740689