Kaolin clotting time

A laboratory test for evaluating blood coagulation

Kaolinite mineral used in the test

The Kaolin Clotting Time (KCT) is a laboratory test used to evaluate the intrinsic pathway of the coagulation cascade. It is particularly useful in the detection of lupus anticoagulant, a type of antiphospholipid antibody that can interfere with normal blood clotting processes.

Principle

The test measures the time it takes for a clot to form in a sample of plasma after the addition of kaolin, a fine white clay that acts as a surface activator. Kaolin provides a negatively charged surface that activates the contact factors of the intrinsic pathway, specifically factor XII (Hageman factor), leading to the conversion of factor XI to its active form. This activation cascade ultimately results in the formation of a fibrin clot.

Procedure

In the KCT, a sample of citrated plasma is mixed with kaolin and incubated at 37°C. The time taken for clot formation is measured. The presence of lupus anticoagulant prolongs the clotting time, as these antibodies interfere with phospholipid-dependent coagulation reactions.

Clinical Significance

The KCT is primarily used to detect the presence of lupus anticoagulant, which is associated with an increased risk of thrombosis and pregnancy complications. It is often used in conjunction with other tests such as the activated partial thromboplastin time (aPTT) and the dilute Russell's viper venom time (dRVVT) to confirm the presence of antiphospholipid antibodies.

Limitations

While the KCT is sensitive to lupus anticoagulant, it is not specific and can be affected by other factors such as deficiencies in coagulation factors or the presence of other inhibitors. Therefore, it is important to interpret the results in the context of other clinical and laboratory findings.

Related Pages

• Coagulation
• Lupus anticoagulant
• Antiphospholipid syndrome
• Activated partial thromboplastin time
• Dilute Russell's viper venom time