APTT (blood clotting test): when to perform it and how to interpret the results?

One of the blood indicators used to assess blood clotting is the APTT (kaolin-cephalin time). The APTT test is used to check for suspected thrombosis, to see how well heparin is working, and to see if someone is bleeding a lot, like when they have nosebleeds or heavy periods. Prolonged APTT may indicate hemophilia, liver cirrhosis, or a lack of vitamin K.

The APTT test measures the activity of XII, XI, X, IX, VIII, V, II, I, high molecular weight kininogen, and prekallikrein, which are all part of the intrinsic pathway of activation of the coagulation system. It is performed by taking a blood sample from a vein in the elbow and measuring the clotting time after adding reagents. Another important indicator of blood coagulation is the INR.

Indications for APTT

The indications for the APTT test are:

  • assessment of treatment with heparin (an anticoagulant),
  • planned surgery, invasive procedures, involving violation of the body’s integuments,
  • bleeding, hemorrhages (manifesting, for example, as prolonged menstruation, , tendency to bruise, petechiae, or frequent or profuse nosebleeds ),
  • thrombosis,
  • intravascular coagulation.

The APTT is a vital test that is conducted during pregnancy. Blood coagulation issues increase the likelihood of bleeding, such as from the vaginal tract, and may result in miscarriage. The APTT test is recommended before pregnancy as part of a preventive screening.

Because practically all blood clotting factors are created in the liver with the help of vitamin K, the APTT test can also be used to diagnose liver illnesses such as cirrhosis or hepatitis, as well as vitamin K insufficiency. (Learn more about vitamin K insufficiency symptoms.) You should avoid stress and physical effort before the assessment and eat on an empty stomach.

APTT – norm

Gender and age have no bearing on the exact APTT timing. The average time is 26-40 seconds. The results take into account the reagent type as well as laboratory requirements. Extended APTT is applicable to people who use anticoagulants, so the laboratory assessing the blood sample should take this into account and provide alternative standards. The APTT in heparin patients is considered to be 1.5-3 times longer than the usual norm.

What does a high APTT mean?

Prolonged  kaolin-cephalin time is characteristic of some diseases. It is also normal for people to take anticoagulants.

If the APTT time is too high , it may indicate:

  • hemophilia ,
  • deficiencies of coagulation factors,
  • vitamin K deficiency,
  • liver diseases,
  • Willebrand’s disease
  • disseminated intravascular coagulation (DIC),
  • lupus (due to the presence of lupus anticoagulants).

What does low APTT mean?

A too-short APTT is characteristic of people with hypercoagulability, which is most often congenital. Some diseases can be accompanied by hypercoagulability. These are:

  • cancers,
  • hypothyroidism ,
  • nephrotic syndrome,
  • thromboembolism .

An APTT that is too low can lead to dangerous blockages . Patients at risk after surgery and women using oral hormonal contraceptives for a long time are at risk. Smokers and people with a family history of congestion are also at risk. Abnormal results usually require re-testing . Interpretation is always up to the doctor.

How to improve blood clotting?

If your APTT score is abnormally high, consult your doctor and follow the drugs he has prescribed. Consume extra vitamin K-rich foods to improve blood coagulation. It’s abundant in green leafy plants like kale and spinach. Note that fats are required for effective absorption of this substance, therefore include them on the dish as well.

In the case of hypercoagulability, you should also take medications as prescribed by a specialist. In addition, a healthy diet, rich in fruits, vegetables and whole grains, is important.


Author: DoctorMaryam.org

4th Professional Medical Student. Karachi Medical and Dental College.

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