Protein S Test

Protein S is among the vital proteins of the human body and it prevents blood clotting. The clotting ability of the blood is very much crucial as it inhibits the excessive blood loss during injury. The Protein S test helps to know the amount of the protein in someone’s blood. The doctor may prescribe this test if someone has developed a blood clot in legs or lungs or if a lady has been through unexplained miscarriages. The human body needs coagulants as well as anticoagulants and Protein S is one of the anticoagulants of the body.

Certain medications, as well as medical conditions, can influence the test result. So it's important for the patient to inform the doctor and healthcare provider about the complete medical history and current medicines. The doctor may ask to stop certain medications (blood thinners or medicines with anticoagulants for at least 2 weeks) before the test. It's recommended not to change or stop any medication without asking the doctor. The level of this protein drops during pregnancy, HIV infection, liver disease etc.

• Tests for Protein S helps to investigate a possible 'excessive clotting disorder’ or hypercoagulable disease. It’s also important to diagnose the reason for an inappropriate blood clot in deep venous thrombosis or venous thromboembolism.
• Several miscarriages may prompt the physician to check the clotting factors of the body.
• There are certain medical conditions like infection, Vitamin K deficiency, HIV/AIDS, pregnancy, sickle cell anemia, liver disorders which can lower the protein S levels. Anticoagulants like Warfarin also drops it.
• In some cases, this deficiency is inherited. In such case, this test is helpful to check the history of blood clots in the family.
• Normal values range from 60-150% inhibition. Abnormalities may indicate the excess blot clotting. The levels of protein S rises with age, although it's not harmful to health.
For those with inherited deficiency, the doctor may prescribe lifestyle changes like quitting smoking and encourage more exercises, maintaining a healthy diet for an optimal level of this protein.

The test should be performed during active clotting event as a blood clot can naturally decrease the protein S levels and make the test inaccurate. A blood sample is collected from an arm vein after wrapping an elastic band around the upper arm. A disposable syringe is inserted into one of the veins to collect the blood in a vial. A minor stinging sensation may be felt which will go away. A cotton ball is placed on the puncture site.