Activated protein C resistance test

Activated Protein C Resistance Test is a blood test used to diagnose Activated Protein C Resistance (APCR), a genetic or acquired condition that increases an individual's risk of blood clot formation. This condition is most commonly associated with Factor V Leiden, a genetic mutation. The test measures the ability of Activated Protein C (APC) to inactivate Factor V, a crucial step in the regulation of blood clotting. An abnormal result indicates a higher risk of developing thrombosis, including deep vein thrombosis (DVT) and pulmonary embolism (PE).

Overview

Activated Protein C Resistance Test is critical in the evaluation of patients with a personal or family history of venous thromboembolism. The test is performed on a blood sample, usually taken from a vein in the arm. It involves adding APC to the patient's plasma and measuring the extent to which APC can prolong clotting time. A reduced response to APC indicates resistance and, consequently, a higher risk of clot formation.

Indications

The test is indicated for individuals who:

• Have a personal or family history of venous thromboembolism
• Have unexplained thrombosis at a young age
• Are considering certain types of hormone therapy or contraception that may increase the risk of clotting
• Are pregnant or planning pregnancy, and have a history of miscarriages or thrombosis

Procedure

The procedure for the Activated Protein C Resistance Test involves:

1. Collection of a blood sample from the patient.
2. Addition of Activated Protein C to the patient's plasma.
3. Measurement of clotting time in the presence and absence of APC.
4. Calculation of the APC resistance ratio, comparing the clotting times.

Interpretation

A lower APC resistance ratio indicates resistance to Activated Protein C, suggesting an increased risk of thrombosis. The presence of Factor V Leiden mutation is confirmed through genetic testing, which may be recommended following an abnormal Activated Protein C Resistance Test result.

Limitations

The test may have limitations, including:

• Not detecting all causes of APC resistance
• Variability in test performance between laboratories
• Possible interference by anticoagulant medications

Management

Individuals diagnosed with Activated Protein C Resistance may require:

• Regular monitoring for signs of thrombosis
• Consideration of anticoagulant therapy, especially in high-risk situations
• Lifestyle modifications to reduce thrombosis risk

Conclusion

The Activated Protein C Resistance Test is a valuable tool in the diagnosis and management of individuals at increased risk of thrombosis due to APC resistance. Early identification and management of this condition can significantly reduce the risk of serious thrombotic events.

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