What is Protein S Functional Activity?
If a clotting event, such as deep vein thrombosis, has occurred or a pregnant patient is showing signs of preeclampsia, a series of protein blood tests may be ordered, including the Protein S Functional Activity test. The Protein S test will be run concurrently with the Protein C test. While different disease processes and/or conditions affect Protein S and Protein C differently, some affect both and can only be revealed if the test results are viewed together.

Normal Value Range

  • Negative Pregnancy Adult: 65 to 140 percent
  • Pregnancy Trimester One: 57 to 95 percent
  • Pregnancy Trimester Two: 42 to 68 percent
  • Pregnancy Trimester Three: 16 to 42 percent

If a pregnant woman tests below the percentages listed above and she is experiencing symptoms of preeclampsia, further medical intervention could be needed to save the life of the fetus and pregnant mother.

If pregnancy is not an issue, low levels of Protein S could be a sign of autoimmune disease, kidney disease, liver disease, infection or vitamin K deficiency. Protein S levels will likely measure lower than normal if a patient is on blood thinners.

< Laboratory Values During Pregnancy