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Kaolin-Kephalin Time is a test that measures the clotting time of plasma in the presence of cephalin and calcium ions after activation with kaolin clay. The test is performed when a deficiency of coagulation factors (II, V, VIII, IX, X, XI, XII) and fibrinogen is suspected. Another indication is also the diagnosis of congenital and acquired bleeding disorders.
Kaolin-Kephalin Time is one of the parameters used to evaluate the processes responsible for blood clotting (haemostasis). In the results of the study, the kaolin-kephalin time is denoted as APTT (Activated Partial Thromboplastin Time), i.e. the time of partial thromboplastin after activation.
APTT measurement is performed for medical indications, e.g. in the diagnosis of systemic lupus erythematosus and antiphospholipid syndrome, or as part of monitoring the treatment of haemophilia.
The test of kaolin-kephalin time consists in measuring the coagulation time of blood in the presence of kefalin and calcium ions after prior activation with kaolin clay. The test is used to assess the intrinsic pathway of clotting activation. They are also performed to monitor treatment with heparin and to diagnose congenital and acquired bleeding disorders.
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As a result of the stimulation of the coagulation system, a series of cascade reactions lead to the formation of a clot, which protects the body against blood loss from the damaged vessel. Proteins activated with the participation of substances derived from tissues (externally) or vessels (intrinsically) take part in the cascade. Both pathways connect and together they cut fibrin fibers from fibrinogen, which close the lumen of the damaged vessel and form a clot. For the proper process of formation of a stable clot, it is necessary that both coagulation pathways and the right amount of individual clotting factors should work together. They are stimulated as a result of vessel trauma. Clotting factor deficiencies (congenital or acquired) lead to the formation of an unstable clot and prolonged bleeding. An excess of clotting factors in turn leads to thrombosis.
The kaolin-kephalin time is the time required for the formation of a clot after the stimulants of the intrinsic cascade have been added to the plasma.
Vitamin K is needed for proper blood clotting. It is naturally produced in the large intestine and the liver.
It is also found in foods such as lettuce, green vegetables, cauliflower, kale, Brussels sprouts or asparagus. Vitamin K can also be found in strawberries, tomatoes and even avocados. Therefore, it is recommended to follow a diet with plenty of these ingredients.
The most important indications for the kaolin-kephalin time test are listed below.
- Suspected deficiencies of coagulation factors (II, V, VIII, IX, X, XI, XII) and fibrinogen.
- Suspicion of disseminated intravascular coagulation.
- Monitoring unfractionated heparin treatment (e.g. in the treatment of thromboembolism).
- Routine assessment before surgery – the purpose of the examination is to exclude the risk of bleeding.
- Diagnostics of congenital and acquired bleeding disorders (diagnosis and disease control).
- Controlling the administration of coagulation factors in patients with haemophilia.
APTT measurement – test price
The kaolin-kephalin time test can be performed on the basis of a referral by a doctor, but only if he has a contract with the National Health Fund. The test is then fully refunded. Performing APTT privately it costs from 6 to 15 PLN. However, a single APTT test is rarely performed, usually the entire coagulation system and other parameters are measured. The price of a coagulogram is about PLN 30.
Kaolin-kephalin time – preparation and course of the study
The study of kaolin-kephalin time does not require special preparations. The test is performed with a standard fasting blood sample from a vein in the arm.
Material for APTT testing: citrate or platelet poor plasma (i.e. collected in a test tube with 3,8% sodium citrate solution, which aims to bind calcium ions and inhibit the clotting process). Then, kaolin and cephalin phospholipid are added to the plasma prepared in this way. Finally, calcium chloride is added and the time until a blood clot forms in the tube is measured.
Preparation for the examination: fasting (at least 8 hours). It is recommended to appear refreshed after a night’s sleep at the collection point. Within XNUMX hours before performing the test, you should not undertake intense physical activity, and the issue of taking medications (especially for chronic diseases of the circulatory system) should be discussed with your doctor.
The course of the study: single blood sampling from a vein in adults. In children, a small lancet incision is made in the skin to cause light bleeding. Then the collected material is sent for further laboratory analysis.
Time to wait for the result: 1 Day.
Standard: approx. 26–46 seconds, but it depends on the individual laboratory determinations. In people taking heparin, the kaolin-kephalin time may be extended up to 100 seconds. It should also be remembered that APTT is longer in children and it decreases with age.
Kaolin-Kephalin Time is a measure of the excitation of the endogenous clotting system. The test result may depend on the reagents used, therefore there are different reference values in different laboratories. In any case, the result should be consulted with a doctor.
In most cases, the assessment of the patient’s condition is possible only with a set of tests appropriately selected by the doctor. APTT is only one of the parameters used in the study of the coagulation system – coagulogram. Others parameters determined in the coagulation process, are:
- prothrombin time (PT);
- thrombin time (TT);
- Bartoxobin time (RT);
- fibrynogen;
- antytrombina III.
APTT above normal – interpretation of results
The APTT test is performed to determine if there has been an increase in kaolin-kephalin time. Typically, the measurement is performed in parallel with testing for prothrombin time or other parameters to provide a complete picture of possible bleeding disorders. Additionally, a medical history is necessary for the interpretation of the test. If it does not indicate a likelihood of abnormality, and the measurement is still not normal, the tests may need to be repeated.
The cause of an incorrect APTT result may be errors in the analysis of the sample.
Increased kaolin-kephalin time is characteristic of the following ailments:
- haemophilia type: A (blood coagulation factor VIII deficiency); B (congenital lack of blood clotting factor IX); C (congenital deficiency of blood clotting factor XI),
- von Willebrand disease (the cause of its occurrence is the deficiency of von Willebrand factor, which is responsible for the proper adhesion of platelets),
- deficiency of clotting factors X, fibrinogen and prothrombin (seen in liver diseases),
- DIC syndrome (disseminated intravascular coagulation),
- treatment with heparin, warfarin or acenocoumarol,
- deficiency of fibrinogen in the blood serum and the presence of pathological fibrinogen,
- liver damage
- lupus erythematosus,
- coagulation factor V deficiency (congenital or acquired),
- vitamin K deficiency
APTT below normal – interpretation of results
A shortened kaolin-kephalin time may indicate activation of the clotting process, but this condition is also observed in blood coagulability. It occurs, inter alia, in rheumatoid arthritis, intestinal inflammation, taking chemotherapy and some cancers, e.g. leukemia. Excessive blood clotting is also a symptom of thrombophilia, a congenital disorder of blood clotting. Reduced APTT time can also occur when the test is poorly performed.
Although truncated APTT occurs in some conditions, additional tests are required for diagnostic purposes. Post-activation partial thromboplastin time results are not considered a significant parameter in the diagnosis of hypercoagulable conditions.
Do you need interpretation of test results? Are you worried about your symptoms? Contact your doctor. Make an online teleconsultation with your family doctor at haloDoctor.pl to get answers to your questions.
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