P-APT time (APTT) – Blood test for coagulation and bleeding risk
P-APT time (APTT), or activated partial thromboplastin time, is a functional test that measures how quickly the blood coagulates via the intrinsic coagulation system. The analysis is performed by activating coagulation in plasma with specific substances and measuring the time until a clot forms. The result is used, among other things, to investigate bleeding disorders and to monitor treatment with anticoagulant medications such as heparin.
Why analyze P-APT time (APTT)?
An APTT blood test is used to assess the blood’s ability to clot and to identify risks of bleeding or thrombosis. It is particularly important during treatment with unfractionated heparin, where APTT is used to ensure that the blood does not become too thin or too viscous. The test is also central when hemophilia, von Willebrand disease, or other factor deficiencies are suspected. Since many coagulation factors are produced in the liver, APTT is also used as part of investigations into liver function.
Analysis of P-APT time (APTT) is recommended to:
- Monitor and adjust dosage during treatment with heparin.
- Investigate suspected coagulation disorders, such as hemophilia or von Willebrand disease.
- Assess the liver’s ability to synthesize coagulation factors.
- Evaluate bleeding risk before surgery or medical procedures.
Why is APTT important?
Coagulation is a central part of the body’s defense system, enabling bleeding to stop through the formation of a blood clot. For this process to work, the coagulation factors in the blood must function together properly. In summary, APTT is an important analysis for assessing both bleeding risk and underlying conditions that affect blood coagulation.
What does a high or low P-APT time (APTT) mean?
- Prolonged APTT: Indicates slower coagulation. This may be seen with coagulation factor deficiencies, hemophilia, liver disease, vitamin K deficiency, heparin treatment, or the presence of antibodies that affect coagulation.
- Normal APTT: Usually 20–30 seconds (may vary slightly between laboratories). A normal value means that coagulation is functioning properly but does not completely rule out mild deficiencies.
- Shortened APTT: Rare, but may indicate increased coagulation activity, for example during inflammation, pregnancy, or thrombotic conditions.
