EXTEM refers to a specific diagnostic test used in medical settings to evaluate blood clotting.
Understanding the EXTEM Assay
The EXTEM assay is a semi-quantitative in vitro diagnostic assay used to monitor the coagulation process via the extrinsic pathway in citrated whole blood specimens on the ROTEM™ delta. This definition comes directly from the provided reference.
In simpler terms, EXTEM is a laboratory test performed on a sample of a patient's blood (specifically, whole blood treated with citrate to prevent clotting before testing). Its main purpose is to assess how well the blood clots when initiated through the extrinsic pathway of coagulation. It's called "semi-quantitative" because it provides data points that reflect the rate and strength of clot formation, rather than a single absolute quantity like the amount of a specific substance. The test is performed using a specialized instrument, such as the ROTEM™ delta device mentioned in the reference.
Key Features of EXTEM
- Type of Test: Semi-quantitative, in vitro (outside the body) diagnostic assay.
- Sample Type: Citrated whole blood.
- Pathway Tested: Primarily the extrinsic pathway of coagulation. This pathway is typically initiated when blood comes into contact with tissue factor, which is released from damaged tissues.
- Purpose: To monitor the coagulation process.
- Device: Performed on specialized coagulometers like the ROTEM™ delta.
Why is EXTEM Used?
Clinically, EXTEM is often used as part of a comprehensive panel of tests (like those performed on ROTEM™ or TEG™ devices) to evaluate a patient's hemostatic status, particularly in critical care settings, surgery, or trauma. It helps clinicians understand if a patient has a problem with their ability to form a clot via the extrinsic pathway, which can be crucial for guiding targeted treatment with blood products or clotting factors.
How it Works (Simplified)
During the EXTEM test, a substance that activates the extrinsic pathway (tissue factor) is added to the citrated whole blood sample. The device then continuously measures the viscosity or elasticity of the blood as it clots over time. Key parameters measured might include:
- Clotting time (how long it takes for the clot to start forming)
- Clot formation speed (how quickly the clot strengthens)
- Maximum clot firmness (how strong the final clot is)
- Clot lysis (if the clot breaks down too quickly)
These parameters provide insights into potential deficiencies in clotting factors (like Factor VII) or issues with fibrinogen and platelet function within the extrinsic pathway.
Summary Table
| Feature | Description |
|---|---|
| What it is | Semi-quantitative in vitro diagnostic assay |
| Purpose | Monitor the coagulation process |
| Pathway | Extrinsic pathway |
| Sample | Citrated whole blood |
| Device | Performed on ROTEM™ delta (or similar viscoelastic testing device) |
In essence, EXTEM is a critical tool for assessing a specific part of the body's complex blood clotting system, providing rapid, actionable information in situations where bleeding or clotting disorders are a concern.
