What is the significance of PT and aPTT?

The aPTT test is used when someone has unexplained bleeding or clotting. Along with the PT test (which evaluates the extrinsic and common pathways of the coagulation cascade), the aPTT is often used as a starting place when investigating the cause of a bleeding or thrombotic (blood clot) episode.

What are 5 factors that influence PT?

The prothrombin time is made longer by:

• Blood-thinning medicine, such as warfarin.
• Low levels of blood clotting factors.
• A change in the activity of any of the clotting factors.
• The absence of any of the clotting factors.
• Other substances, called inhibitors, that affect the clotting factors.

What factors affect PT and PTT?

Common causes of prolonged PT and/or APTT are the use of oral anticoagulants or heparin, vitamin K deficiency and liver disease. Other causes include coagulation factor deficiencies, coagulation factor inhibitors and diffuse intravascular coagulation.

Which factor deficiency is associated with a prolonged PT and aPTT?

If, for example, both the PT and aPTT are prolonged, the defect is probably in the common clotting pathway, and a deficiency of factor I, II, V, or X is suggested. A normal PT with an abnormal aPTT means that the defect lies within the intrinsic pathway, and a deficiency of factor VIII, IX, X, or XIII is suggested.

What are the activators that can be used in aPTT test?

Activated partial thromboplastin time (APTT) is widely used as a test for LA screening. APTT reagents are composed of activators, such as silica or ellagic acid, and phospholipids, and APTT reagents with silica are recommended for LA screening because of greater sensitivity.

Why are PT tests done on patient samples?

Why Are PT Tests Done? Doctors do PT tests to check for bleeding problems. A child might have the test if they’ve had a lot of bleeding or bruising, have a medical condition that can lead to problems with clotting, or are having surgery or a procedure that might cause bleeding.

What can cause elevated aPTT?

CAUSES

• Lupus anti-coagulant (antiphospholipid syndrome)
• Heparin exposure.
• Haemophilia A and B (Factor VIII and IX deficiency respectively)
• Factor XII deficiency.
• Factor XI deficiency.
• Contact factor deficiency e.g. prekallikrein (not clinically important)
• Artefact (incorrect amount of blood in the tube)

How do you do PT and aPTT?

To perform the test, the phlebotomist or nurse takes a sample of blood from your arm. They clean the site with an alcohol swab and insert a needle into your vein. A tube attached to the needle collects the blood. After collecting enough blood, they remove the needle and cover the puncture site with a gauze pad.

What causes a high prothrombin time?

Liver problems. Inadequate levels of proteins that cause blood to clot. Vitamin K deficiency. Other substances in your blood that hinder the work of clotting factors.

How do you do PT and APTT?

What might cause a prolonged prothrombin time?

Causes of prolonged PT include the following: Warfarin use. Vitamin K deficiency from malnutrition, biliary obstruction, malabsorption syndromes, or use of antibiotics. Liver disease, due to diminished synthesis of clotting factors.

What are the coagulation factors affected by prolonged PT?

PT measures the activity of VII, X, V, II, and fibrinogen. If aPTT is normal, then a prolonged PT is due to factor VII deficiency. PT is relatively insensitive to minor reductions in the clotting factors. aPTT is prolonged with deficiencies of XII, XI, X, IX, VIII, V, II, and fibrinogen.