Laboratory test for predisposition to thrombosis (thrombophilia)

Blood clotting is caused by the complex action of several blood clotting factors (proteins). If the balance is upset due to a lack or defect in any of the units, haemophilia or unwarranted blood clotting (thrombosis) develops. Defects are usually caused by some genetic abnormality, increasing the predisposition to thrombosis.

Thrombophilia can be screened, and genetic abnormalities in proteinaceous substances involved in blood clotting can be detected by blood tests.

The laboratory package for the predisposition to thrombosis includes the following tests:

• Protein C: a component of the system that prevents excessive blood clots. With its help, blood clotting takes place only at the site of the injury and only lasts as long as it is needed, after which it dissolves. Protein C regulates the process of dissolving the clot. Low levels in the blood indicate excessive blood clots, increasing the predisposition to thrombosis.
• Protein S: another component of the system that prevents excessive blood clots, it regulates the dissolution of blood clots with Protein C. Low levels in the blood indicate excessive blood clots and predisposition to thrombosis.
• Anti-thrombin III: obstructs the action of a number of blood clotting factors, preventing excessive or inadequate clotting. Its low levels increase blood clotting.
• Prothrombin time: used to test blood clotting. It shows the function of the enzyme system that initiates blood clotting. The prothrombin time shows how long it takes for the clot to form. Lower levels may lead to increased haemophilia.
• APTT (activated partial thromboplastin time): monitors the function of one of the enzyme systems that regulates blood clotting. It measures the time that passes until clotting.
• Prothrombin gene mutation: one of the most important genetic risk factors for the development of venous thrombosis. As a result of the gene mutation, the activity of the coagulation system is increased, thus increasing the predisposition for both venous and arterial thrombosis. The gene mutation may be present in heterozygous (containing one normal and one mutant gene) and homozygous (containing two mutant genes) form. The homozygous form is rare, but in its presence shows that the predisposition to thrombosis is 25 times more of the normal.
• Lupus anticoagulant: a functional test for phospholipid antibodies that increase the susceptibility to thrombosis. Lupus anticoagulant positivity increases the predisposition to thrombosis and can cause miscarriages.
• Phospholipid antibodies: inhibit the activity of phospholipid proteins in the coagulation process, which can lead to coagulation disorders, vascular occlusion.
• APC resistance: is used to detect the most common genetic predisposing factor for thrombosis, the Leiden mutation. Due to the mutation, the protein chain of activated coagulation factor V cannot be broken down by an enzyme called activated protein C (APC). Due to the slowing down of the breakdown of coagulation factors, patients have increased blood clotting and are therefore prone to thrombosis.
• Homocysteine: it is normally present in very small amounts in the body, its elevated value can cause vascular disease in any organ, most often the heart (myocardial infarction, coronary heart disease) and the brain (stroke).

How do I prepare for the test?

When is the result expected?