This test evaluates the function of Protein S, a vitamin K–dependent protein that works alongside Protein C to control clot formation. Together, they help prevent excessive clotting by regulating thrombin generation.
Diagnostic Value: Low Protein S activity suggests Protein S deficiency, which can be inherited or acquired (for example, due to pregnancy, oral contraceptives, or liver disease).
Clinical Significance: Deficiency increases the risk of venous thromboembolism, DVT, or PE, and may also play a role in pregnancy-related complications.
Symptom Correlation: Patients may have leg pain or swelling, chest pain, or recurrent miscarriages.
The Protein S Activity test provides essential information for evaluating clotting disorders and assessing overall anticoagulant balance.