Overview
Factor XIII is a clotting protein that plays a key role in the last stage of blood clot formation. It is also known as the Fibrin-Stabilizing Factor. Unlike other clotting factors that help initiate clotting, Factor XIII works after a soft clot has already formed, making it stronger, more stable, and resistant to breaking down.
The Factor XIII Test measures the amount or activity of this protein in the blood. It is commonly used to evaluate unexplained bleeding, delayed bleeding, poor wound healing, and certain pregnancy complications. It helps diagnose both inherited and acquired Factor XIII deficiency, a rare but serious bleeding disorder.
What is the Factor XIII Test?
The Factor XIII Test checks:
- Factor XIII activity (how well it works)
- Factor XIII antigen (how much is present)
This test is usually ordered when:
- A person has normal routine clotting tests (PT, aPTT are normal) but still bleeds
- There is delayed bleeding after injury or surgery
- A child has unexplained bleeding episodes
- A woman has recurrent miscarriages
- Wounds heal poorly
- Intracranial bleeding happens without trauma
Factor XIII deficiency is rare but dangerous because bleeding may not appear immediately—it often starts hours after an injury, when a weak clot dissolves.
Where is Factor XIII Produced in the Body?
Factor XIII is produced in multiple areas:
1. Liver
Major source of Factor XIII production.
2. Bone Marrow
Especially from cells involved in clotting and healing.
3. Monocytes
White blood cells that contribute to inflammation and repair.
4. Platelets
Store and release Factor XIII at the site of an injury to strengthen the clot.
Main Functions and Importance of Factor XIII
Factor XIII has several critical roles in the clotting system and overall body function:
1. Strengthens and Stabilizes Clots
After initial clot formation, Factor XIII:
- Cross-links fibrin strands
- Converts a soft gel-like clot into a firm, stable clot
- Prevents premature clot breakdown
2. Helps in Wound Healing
Factor XIII helps tissue repair by stabilizing the clot and supporting early healing.
3. Maintains Pregnancy
Factor XIII strengthens the attachment of the placenta to the uterus.
Deficiency can lead to recurrent miscarriages.
4. Prevents Delayed Bleeding
While many clotting factors prevent immediate bleeding, Factor XIII prevents late bleeding—bleeding that happens after hours or even a day.
Causes of Low Factor XIII Levels
Low levels may be inherited or acquired.
1. Inherited Factor XIII Deficiency
A rare genetic disorder passed through families.
Babies may bleed from the umbilical stump or in the brain.
2. Liver Disease
Liver damage reduces production of multiple clotting proteins, including Factor XIII.
3. Autoimmune Disorders
The immune system forms antibodies that attack and destroy Factor XIII.
4. Severe Infections / DIC
In widespread clotting conditions (like DIC), clotting factors—including Factor XIII—are used up rapidly.
5. Certain Medications
Some drugs affect clotting factor production or function.
Symptoms of Low Factor XIII Levels
Symptoms of low Factor XIII include:
- Delayed bleeding after surgery or injury (unique feature)
- Recurrent miscarriages in women
- Easy bruising
- Bleeding from the umbilical cord in newborns
- Poor wound healing
- Soft tissue or muscle bleeding
- Intracranial bleeding (dangerous and can occur without trauma)
Bleeding may be mild in some and severe in others depending on the level of deficiency.
Causes of High Factor XIII Levels
Factor XIII is rarely tested for high levels because excess usually does not cause major issues.
However, mild increases may occur in:
- Pregnancy
- Inflammation
- After tissue injury
These increases are generally normal and not considered harmful.
Symptoms of High Factor XIII Levels
High Factor XIII:
- Usually causes no symptoms
- Does not significantly increase clot risk
- Does not typically require treatment
Reference Ranges
Factor XIII activity level:
50% – 150% of normal activity
Ranges vary depending on:
- Age
- Laboratory method
- Test type (activity vs antigen)
Levels below 5% indicate severe deficiency.
Sample Type
- Venous blood sample (arm vein)
- Collected in a Light Blue Top Tube
- Additive: Sodium Citrate
- Purpose: Prevents clotting inside the tube so the lab can measure Factor XIII activity accurately
Test Preparation
- No fasting required
- Avoid heavy exercise before testing
- Tell your doctor if you are taking:
- Blood thinners
- Steroids
- Anti-inflammatory medications
- Inform if you have:
- Liver disease
- Recent major infection
- History of recurrent miscarriages
- Family history of bleeding disorders
When to Consult a Doctor
You should seek medical advice if you experience:
Bleeding Symptoms
- Bleeding that starts hours after injury
- Excessive bleeding after surgery or dental procedures
- Frequent bruising
- Poor wound healing
- Heavy menstrual bleeding
- Nosebleeds
Pregnancy Concerns
- Recurrent miscarriages
- Abnormal bleeding during pregnancy
Serious Symptoms (Emergency)
- Severe headache or vomiting (possible brain bleed)
- Weakness or confusion
- Sudden back or abdominal pain
- Bleeding that does not stop
Factor XIII deficiency requires urgent attention because bleeding complications can be dangerous.
Important Word Explanations
- Factor XIII: A clotting protein that stabilizes the clot
- Fibrin: Protein strands forming the framework of a clot
- Cross-linking: Strengthening fibrin strands to stabilize the clot
- DIC: A condition causing uncontrolled clotting and bleeding
- Antigen: Amount of protein present
- Activity Test: Measures how well the protein works
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