Overview
Fibrin Degradation Products (FDP) are small protein fragments that appear in the blood when a blood clot breaks down. FDPs are released during the natural process of fibrinolysis, where the enzyme plasmin dissolves fibrin, the protein mesh that forms a stable blood clot. Measuring FDP levels helps doctors diagnose conditions related to excessive clotting, overactive clot breakdown, or serious bleeding disorders such as DIC (Disseminated Intravascular Coagulation).
FDP testing is important in emergency medicine, intensive care, trauma management, and the evaluation of clotting abnormalities.
What Are Fibrin Degradation Products (FDP)?
When a blood clot forms, fibrin creates a stable mesh that seals the injured blood vessel. Once healing begins, the body dissolves this clot using plasmin. As plasmin breaks fibrin into pieces, these fragments enter the bloodstream and are called Fibrin Degradation Products.
High FDP levels indicate that the body is forming and breaking down many clots at the same time. This is a hallmark of conditions like DIC, major trauma, blood clots in the veins or lungs, and some cancers.
Doctors often order FDP along with D-dimer to evaluate clotting and bleeding disorders.
Where Are FDPs Produced in the Body?
FDPs are not produced by any organ. Instead, they are formed as a result of:
1. Fibrin Clot Formation
When fibrin forms a clot after injury.
2. Fibrinolysis
The body naturally breaks down clots through:
- Plasmin (main enzyme)
- Fibrinolytic pathway (clot-dissolving system)
During this process, FDPs are released into the bloodstream.
Thus, FDPs are simply a result of clot breakdown, not a substance made intentionally by the body.
Main Functions and Importance of FDP Testing
Although FDPs themselves have no active function, testing their levels is extremely important in diagnosing critical medical conditions.
1. Detects Excessive Clot Formation and Breakdown
High levels indicate active clotting followed by rapid breakdown.
2. Helps Diagnose Disseminated Intravascular Coagulation (DIC)
DIC is a life-threatening emergency where clots and bleeding occur simultaneously. FDP is a key diagnostic marker.
3. Helps Identify Venous Blood Clots
FDP rises in:
- Deep Vein Thrombosis (DVT)
- Pulmonary Embolism (PE)
Often used along with a D-dimer test.
4. Monitors Fibrinolytic Therapy
Used to check the effectiveness of clot-dissolving medications (e.g., tPA).
5. Differentiates Types of Bleeding Disorders
Helps determine whether bleeding is due to:
- Clotting factor deficiency
or - Excessive clot breakdown
This distinction guides treatment.
Causes of Low/Negative FDP Levels
Low or undetectable FDP levels indicate:
1. Normal Body Function
Healthy individuals have very low FDP levels (<10 mcg/mL).
2. No Excessive Clotting or Fibrinolysis
Means the body is not actively forming or breaking down clots abnormally.
Thus, low FDP is considered normal.
Symptoms of Low/Negative FDP Levels
Low FDP levels do not cause any symptoms and are not associated with disease.
They simply indicate normal clotting activity.
Causes of High/Positive FDP Levels
High FDP levels are a sign of excessive clot formation and breakdown in the body. Common causes include:
1. Disseminated Intravascular Coagulation (DIC)
A severe condition where many tiny clots form, then break down, causing:
- Heavy bleeding
- Organ damage
- Shock
FDP is extremely high in DIC.
2. Deep Vein Thrombosis (DVT)
Blood clot in the deep veins of the legs.
3. Pulmonary Embolism (PE)
A clot that travels to the lungs — a medical emergency.
4. Severe Trauma or Burns
Major tissue injury triggers clotting and breakdown.
5. Liver Disease
The liver cannot clear FDPs properly, leading to elevated levels.
6. Thrombolytic Therapy
Medications used to dissolve blood clots (ex: tPA) result in increased FDP levels.
7. Certain Cancers
Especially cancers of the:
- Lung
- Pancreas
- Stomach
- Blood (leukemia)
These can increase clotting activity.
Symptoms of High/Positive FDP Levels
Symptoms depend on the underlying condition.
Symptoms Seen in DIC
- Easy bruising
- Excessive bleeding
- Oozing from wounds
- Blood in urine or stool
- Organ failure (severe cases)
Symptoms of Blood Clots (DVT/PE)
- Leg pain, swelling, redness (DVT)
- Sudden chest pain (PE)
- Shortness of breath
- Rapid heart rate
Life-Threatening Symptoms
- Shock
- Severe drop in blood pressure
- Multiple organ damage
High FDP levels always require medical evaluation.
Reference Ranges
Normal FDP levels:
Less than 10 mcg/mL
Higher levels indicate:
- Increased clot breakdown
- Possible DIC
- Thrombosis
- Trauma-related clot activity
Reference ranges may differ slightly with each laboratory.
Sample Type
- Venous blood sample
- Tube: Light Blue Top Tube
- Additive: Sodium Citrate
- Purpose: Prevents the blood from clotting in the tube
The lab measures FDP levels from plasma.
Test Preparation
- No fasting required
- Avoid heavy exercise before the test
- Inform your doctor if you take:
- Blood thinners
- Hormonal medicines
- Anti-inflammatory medications
- Notify your doctor if you have:
- Recent surgery
- Severe infection
- Trauma
- Liver disease
This helps interpret the test correctly.
When to Consult a Doctor
Seek medical attention if you have:
Bleeding Symptoms
- Bruising easily
- Bleeding that doesn’t stop
- Bleeding after surgery
- Blood in urine or stool
Clotting Symptoms
- Swollen, painful leg
- Warmth/redness (DVT)
- Sudden breathlessness
- Sharp chest pain (PE)
Severe Symptoms
- Sudden confusion
- Fainting
- Very fast heart rate
- Severe bleeding
- Symptoms of shock
These may indicate serious clotting disorders like DIC.
Important Word Explanations
- Fibrin: Protein that forms a clot
- Fibrinolysis: Breakdown of clots
- Plasmin: Enzyme that dissolves fibrin
- DIC: Life-threatening condition involving clotting + bleeding
- Thrombolytic Therapy: Medications that dissolve clots
- Sodium Citrate Tube: Prevents clotting in the blood sample
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