Protein C and Protein S Test

Protein C and Protein S Test-Why am I having this test?

Protein C and protein S test is used to check for low levels of two proteins that help regulate how and when your blood clots. Proteins C and S stop blood clotting (coagulation) when it should not occur.

The presence and function of proteins C and S in your blood depend on vitamin K. This test may be recommended if your health care provider suspects that you have:

• A blood-clotting disorder.
• A condition in which blood clots form throughout your body’s small blood vessels (disseminated intravascular coagulation, orDIC).

Proteins C and S can also be affected by the medicine warfarin, pregnancy, hormone treatments, or having an active blood clot.

What is being tested?

This test measures the amount of protein C and protein S in your blood and determines whether these proteins are functioning as they should.

What kind of sample is taken?

A blood sample is required for this test. It is usually collected by inserting a needle into a blood vessel or by sticking a finger with a small needle.

Tell a health care provider about:

• All medicines you are taking, including vitamins, herbs, eye drops, creams, and over-the-counter medicines.
• Any medical conditions you have.
• Whether you are pregnant or may be pregnant.

How are the results reported?

These tests measure not only the level of protein C or protein S, but also whether the protein is functioning as it should. Thus, test results are reported as a percentage of normal activity. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference ranges). Reference ranges may vary among labs and hospitals. For this test, common reference ranges are:

• Protein C: 70–150% of normal activity. Protein C levels may be lower in females and decrease with age in both males and females.
• Protein S: 60–130% of normal activity.

What do the results mean?

People with results that are within the reference range usually do not have a clotting problem. Results that are lower than the reference range can indicate a number of health conditions. These may include:

• Inherited deficiency of protein C or protein S.
• DIC. This abnormal blood clotting in small blood vessels can reduce or block blood flow and damage your body’s organs.
• Conditions that cause your blood to clot too often (hypercoagulable states).
• A blood clot that travels to a lung (pulmonary embolism).
• Blood clot in a vein or artery.
• Vitamin K deficiency.
• Sickle cell disease.
• Some autoimmune diseases.
• Inflammation or swelling.
• Complications of taking warfarin, including skin breakdown.
• Some cancers.
• Malnutrition.

Talk with your health care provider about what your results mean.

Questions to ask your health care provider

Ask your health care provider, or the department that is doing the test:

• When will my results be ready?
• How will I get my results?
• What are my treatment options?
• What other tests do I need?
• What are my next steps?

Summary

• The protein C and protein S test is used to check for low levels of two proteins that help regulate how and when your blood clots.
• A blood-clotting disorder may result if levels of protein C and protein S are low.
• Results that are lower than the reference range can indicate a number of health conditions.
• Talk with your health care provider about what your results mean.