Protein C and Protein S Tests

The Protein C and Protein S tests are blood tests used to measure the levels of two proteins in the blood that play a crucial role in the regulation of blood clotting.

What are Protein C and Protein S?

Protein C and Protein S are vitamin K-dependent proteins produced by the liver. They work together as anticoagulants to prevent excessive blood clotting. Protein C is an enzyme that helps to break down blood clots, while Protein S serves as a cofactor for Protein C, enhancing its activity.

Why are these tests performed?

The Protein C and Protein S tests are typically ordered in the following situations:

• To diagnose inherited or acquired disorders that affect blood clotting, such as thrombophilia
• To investigate the cause of recurrent or unexplained blood clots (thrombosis)
• To monitor patients with a history of blood clots who are at risk of developing another clot
• To evaluate the effectiveness of anticoagulant therapy in patients with blood clotting disorders

How are the tests performed?

The Protein C and Protein S tests involve taking a blood sample from a vein, usually in the arm. The blood is then sent to a laboratory for analysis.

What do the test results mean?

The results of the Protein C and Protein S tests are typically reported as a percentage of normal activity or concentration. Abnormal results may indicate:

• Deficiency: Low levels of Protein C or Protein S, which can increase the risk of blood clots
• Dysfunction: Abnormal function of Protein C or Protein S, which can also increase the risk of blood clots
• Normal: Normal levels and function of Protein C and Protein S, which suggests that other factors may be contributing to blood clotting disorders

Reference ranges

The reference ranges for Protein C and Protein S tests vary depending on the laboratory and the specific test used. Generally:

• Protein C: 70-140% of normal activity
• Protein S: 60-150% of normal concentration (free and total)

Limitations and potential interferences

Certain factors can affect the accuracy of the Protein C and Protein S tests, including:

• Vitamin K deficiency or excess
• Warfarin therapy (affects vitamin K-dependent proteins)
• Liver disease or dysfunction
• Pregnancy or estrogen therapy (can increase Protein S levels)

It is essential to consult with a healthcare professional for proper interpretation of test results and to discuss any concerns or questions.

Frequently Asked Questions (FAQs)

What are Protein C and Protein S tests?
Blood tests that measure the levels of Protein C and Protein S in the blood.

Why are these tests ordered?
To diagnose or rule out bleeding or clotting disorders, such as thrombophilia.

What is Protein C?
A protein that helps regulate blood clotting by inactivating certain clotting factors.

What is Protein S?
A protein that helps activate Protein C and regulate blood clotting.

What are normal levels of Protein C and Protein S?
Typically, 70-140% of the normal range for Protein C and 60-150% for Protein S, but may vary depending on laboratory.

What happens if levels are low?
May indicate a higher risk of blood clots or thrombosis, but further evaluation is needed to determine cause.

Can these tests diagnose specific conditions?
May help diagnose conditions such as Protein C deficiency or Protein S deficiency, but additional testing and evaluation are often required.

How are the tests performed?
Typically, a blood sample is drawn from a vein in the arm and sent to a laboratory for analysis.

Are there any risks associated with these tests?
Generally, no significant risks, but may include minor bleeding or bruising at the needle site.

What factors can affect test results?
Certain medications, liver disease, pregnancy, and other medical conditions may affect Protein C and Protein S levels.