APTV (activated partial thromboplastin time)

APTV (activated partial thromboplastin time, also APTT or aPTT in the literature) shows how long plasma takes to clot through one part of the clotting system. It is performed for bleeding tendency, investigation of clotting disorders, monitoring heparin treatment and before certain operations and procedures. It is most often measured together with prothrombin time (PT) and fibrinogen.

Who is this test for

• people who bruise easily, frequently bleed from the nose or gums, bleed for a long time after tooth extraction or injury, or have bleeding into joints;
• women with heavy periods;
• people with a suspected inherited clotting disorder, such as haemophilia A or B or von Willebrand disease, particularly with a family history;
• people being treated with unfractionated heparin, most often in hospital;
• people with recurrent thromboses and women with recurrent miscarriages, when the doctor requests lupus anticoagulant testing;
• people before an operation or procedure, when the doctor considers it appropriate.

What APTV shows

Blood clotting depends on a series of proteins called clotting factors. APTV depends on factors XII, XI, IX and VIII, as well as factors X, V, II (prothrombin) and fibrinogen. When one is deficient or inhibited by a medicine or antibody, clotting time is prolonged.

APTV and PT complement each other. PT is more sensitive to factor VII and warfarin, while APTV is more sensitive to factors VIII, IX and XI and unfractionated heparin. Both tests are therefore usually performed for suspected clotting disorders, alongside fibrinogen and a blood count. APTV results are expressed in seconds and, in some laboratories, as a ratio to normal plasma.

APTV is not mandatory before every procedure. According to guidelines, such as those of the British NICE, clotting tests are not routinely performed in healthy people without a bleeding tendency who do not take anticoagulants. The doctor requests them according to the procedure, diseases (such as liver disease), medicines and personal or family bleeding history. If requested by a surgeon or anaesthetist, they are usually performed as a panel.

Save with a panel

Test aPTT (activated partial thromboplastin time) is also included in these panels.

Coagulation panelPT, aPTT, FibrinogenPrice of individual tests: 28.80€26.00€Details ›Extended coagulation panelPT, aPTT, Fibrinogen, D-dimer, CBC65.00€Details ›

All panels including aPTT (activated partial thromboplastin time) (7) ›

Preparation and sample

Blood is taken from a vein. Fasting is not essential unless PT is also tested that day, for example in the coagulation panel, or glucose and blood fats are tested. Nevertheless, avoid a very fatty meal before collection because it may make the sample cloudy and interfere with measurement.

• If you take anticoagulants such as heparin, warfarin, rivaroxaban, apixaban or dabigatran, do not stop them for blood collection without consulting your doctor.
• State which medicine you take and when you took the last dose, because many of these medicines alter APTV.

How results are interpreted

The reference interval depends on the reagent and instrument and is printed on the report. The doctor interprets results alongside PT, fibrinogen, blood count, medicines and bleeding history.

Prolonged APTV

• Medicines: unfractionated heparin deliberately prolongs APTV, and the doctor determines the target range. Dabigatran may also prolong it, as may other newer oral anticoagulants to a lesser extent, and warfarin. Low-molecular-weight heparin (such as enoxaparin) has little effect on APTV and is not monitored with this test.
• Clotting factor deficiency: haemophilia A (factor VIII) and B (factor IX), von Willebrand disease and factor XI deficiency. In milder von Willebrand disease, APTV may be normal. Factor XII deficiency prolongs APTV but does not cause bleeding.
• Liver disease, vitamin K deficiency and disseminated intravascular coagulation (DIC), usually with prolonged PT.
• Lupus anticoagulant: an antibody that prolongs APTV in the test tube but does not cause bleeding in the body; instead, it is associated with a higher thrombosis risk. It is confirmed with specific tests.

Sometimes the sample itself is responsible, so the doctor usually first repeats a prolonged result in someone without symptoms. Further investigation, such as individual clotting factor measurements, is determined by a haematologist.

Shortened APTV

Shortened APTV usually has no clinical significance. It may occur with acute inflammation and pregnancy, when factor VIII rises, or because of the collection method. It is not used to assess thrombosis tendency.

Urgently seek medical help if bleeding does not stop, if you notice blood in urine or stools, black stools or vomit blood, or have a severe headache after a head injury, particularly if you take anticoagulants.

How to arrange testing

You can come for blood collection without an appointment or referral at one of our branches throughout Croatia (listed on the Contactpage). Prices for all tests and panels are listed in the service price list. Before procedures, APTV is most often included in the Coagulation panel (PT, APTV and fibrinogen), or, when the surgeon requests a broader assessment, the Preoperative panel.

Frequently asked questions

Is APTV the same as APTT or PTT?

Yes. APTV, APTT and aPTT refer to the same test, also commonly abbreviated PTT.

What is the difference between APTV and PT?

Both tests measure clotting time, but each is sensitive to different factors. PT is primarily used to monitor warfarin and assess liver function, while APTV detects deficiencies of factors VIII, IX and XI and monitors unfractionated heparin. They are therefore performed together for suspected clotting disorders.

What does prolonged APTV mean if I take no medicines?

The test most often needs repeating. If prolongation is confirmed, the cause may be a clotting factor deficiency, lupus anticoagulant or liver disease. Your doctor interprets the result with your symptoms and refers you to a haematologist if needed.

Do I need APTV before tooth extraction or a minor procedure?

Generally not if you have no bleeding tendency and do not take anticoagulants. If you take these medicines or have previously bled for a long time, tell your dentist or surgeon, who will assess which tests are needed.