Coagulation Tests Purpose, Procedure, Normal Values and Interpretation
Coagulation Tests, also called Coagulation Profile. A coagulation profile includes PT, aPTT, platelets, fibrinogen, TT, Bleeding Time and D Dimer. This is a screening test for abnormal blood clotting because it examines the factors most commonly associated with a bleeding problem. It does not cover all causes of bleeding tendencies.
Clotting factors are proteins found in the blood that help form blood clots to stop bleeding when injured. These proteins are also called clotting factors. There are several types of clotting factors that play an important role in the formation of blood clots.
Also known as
- Coagulation studies
- Clotting studies
- ‘Coags’
Why Get Tested?
Clotting factor testing is used to determine if you have a problem with one of the clotting factors that can cause your blood to clot too little or too much.
Clotting factor tests are also used to monitor people who have a known problem with clotting factors or who are taking medicines called anticoagulants to reduce the risk of blood clots.
You may need this test if you have:
- An abnormal result from a blood test that measures how long it takes for blood to clot. These tests include a prothrombin time/INR (PT/INR) test and/or a partial thromboplastin time (PTT) test.
- A family history of problems with clotting factors. Some diseases that affect clotting factors, such as hemophilia, are inherited. This means that the child’s parents passed on the gene for the disease. These diseases are not common. A health problem that can affect the clotting factors in the blood:
- Conditions that can cause a clotting disorder include:
- Severe liver disease
- Vitamin K deficiency
- Blood transfusion
- Cancer
- Immune disorders
- Conditions that can cause a blood clot problem include:
- Autoimmune diseases, such as lupus
- Cancer
- Obesity
- Certain infections, such as sepsis and COVID-19
- Not moving for long periods of time, such as after surgery
- Vitamin B6, B12, and folate deficiency
- Symptoms that may be due to a problem with clotting factors:
Symptoms of clotting disorders may include:- Heavy bleeding that does not stop when pressure is applied after an injury, dental procedure, or surgery
- Frequent nosebleeds that start on their own
- Blood in the urine (pee) or stool (poop)
- Easy bruising and large or small red or brown spots under the skin
- Redness, swelling, pain or stiffness due to bleeding in the muscles or joints
- Heavy periods
- Symptoms of excessive blood clotting may include:
- Swelling, redness, warmth and pain in the arms or legs which may be due to a clot
- Difficulty breathing due to a clot that has travelled to the lungs
- Nausea
When to Get Tested?
Bleeding disorders can cause dangerous bleeding or clotting. If your doctor suspects you have a bleeding disorder, he or she may recommend one or more coagulation tests. These tests measure various proteins and how they work.
Conditions that can cause clotting problems include:
- Liver disease
- Thrombophilia, which is excessive clotting
- Hemophilia, which is an inability to clot normally
Coagulation tests are useful for monitoring people who are taking medications that affect the ability to clot. Coagulation tests are also sometimes recommended before surgery.
Tests Includes in Coagulation Profile:
APTT (activated partial thromboplastin time):
Measures part of the clotting pathway called the “intrinsic pathway”; it is compared to a normal blood sample, the “control” value. Increased with intravenous heparin therapy, hemophilia, or DIC.
PT, INR (international normalized ratio):
Measures part of the clotting pathway called the “extrinsic pathway”; increases with warfarin therapy, liver dysfunction, or DIC.
TP measures the time required to generate fibrin after activation of factor VII. It measures the integrity of the “extrinsic” and “common” pathways (factors VII, V, X, prothrombin and fibrinogen).
Platelet count:
The number of platelets in the blood; it is also a routine part of the complete blood count (CBC).
Fibrinogen:
This protein is a precursor to fibrin, which is an essential part of a blood clot. Fibrinogen can be consumed in conditions such as DIC or some snakebite envenomations. Decreased fibrinogen leads to an increased tendency to bleed. D-dimer, which is a product of clot breakdown and increases under conditions of increased clotting activity in the body, is sometimes included but is relatively nonspecific because it is often elevated for a variety of reasons.
As a marker of fibrinolysis, fibrin degradation products (FDPs), also called fibrin breakdown products (FSPs), can be quantified by a latex agglutination-based test. The test uses antibodies against FSPs that are measured by serial dilutions.
Factor V test:
This test measures factor V, a substance involved in clotting. An abnormally low level may indicate liver disease, primary fibrinolysis (clot breakdown), or disseminated intravascular coagulation (DIC).
Thrombin Time (TT):
The thrombin time measures how well fibrinogen works. Abnormal results may be due to inherited fibrinogen disorders, liver disease, certain types of cancer, and medications that affect clotting.
This test measures the time required for the reaction of fibrinogen to fibrin to occur in the presence of thrombin. It measures the integrity of this reaction and isolates an abnormality that may be due to a decrease in normal fibrinogen or to an inhibitor of its activation.
Bleeding time (BT):
This test looks at how quickly the small blood vessels in the skin close and stop bleeding. It is done differently than other blood tests.
By making a small incision in the skin, the hemostatic mechanisms necessary for clotting are activated. Without the help of external pressure, bleeding usually stops within 7 to 9 minutes.
Sample Required for Coagulation Factor Tests:
| Test | Sample Type | Tube/Container | Volume Required |
|---|---|---|---|
| APTT (Activated Partial Thromboplastin Time) | Plasma | Light Blue Top (Sodium Citrate) | 2.7-4.5 mL |
| PT, INR (Prothrombin Time, International Normalized Ratio) | Plasma | Light Blue Top (Sodium Citrate) | 2.7-4.5 mL |
| Platelet Count | Whole Blood | Lavender Top (EDTA) | 2-3 mL |
| Fibrinogen | Plasma | Light Blue Top (Sodium Citrate) | 2.7-4.5 mL |
| Factor V Test | Plasma | Light Blue Top (Sodium Citrate) | 2.7-4.5 mL |
| Thrombin Time (TT) | Plasma | Light Blue Top (Sodium Citrate) | 2.7-4.5 mL |
| Bleeding Time (BT) | Whole Blood (Capillary) | None (Skin puncture) | N/A |
Normal Values of Coagulation Factor Tests:
| Test | Normal Reference Range |
|---|---|
| APTT (Activated Partial Thromboplastin Time) | 25-35 seconds |
| PT (Prothrombin Time) | 11-13.5 seconds |
| INR (International Normalized Ratio) | 0.8-1.2 (for patients not on anticoagulants) |
| Platelet Count | 150,000-450,000/µL |
| Fibrinogen | 200-400 mg/dL |
| Factor V Test | 50-150% of normal activity |
| Thrombin Time (TT) | 14-19 seconds |
| Bleeding Time (BT) | 2-7 minutes (depending on the method used) |
Coagulation Tests Result Interpretation:
- APTT: Prolonged indicates hemophilia, liver disease, or heparin therapy.
- PT/INR: Elevated suggests liver disease, vitamin K deficiency, or warfarin therapy.
- Platelet Count: Low indicates bleeding risk; high suggests clotting risk.
- Fibrinogen: Low indicates DIC or liver disease; high suggests inflammation or pregnancy.
- Factor V Test: Low suggests bleeding disorder; elevated is rare and usually insignificant.
- Thrombin Time (TT): Prolonged indicates fibrinogen deficiency or heparin therapy.
- Bleeding Time (BT): Prolonged suggests platelet dysfunction or vascular disorders.
References:
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- Coagulation Factor Tests | Medlineplus | https://medlineplus.gov/lab-tests/coagulation-factor-tests – (Accessed on Sep 14, 2024)
- Coagulation Profile | Healthingen.com.au | https://healthinfo.healthengine.com.au/coagulation-profile-test – (Accessed on Sep 14, 2024)
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