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Protein S Testing

Protein S: (produced by the liver via Vitamin K-dependent pathway, megakaryocytes, and endothelial cells.)

Function: 60% of PS circulates in an inactive complex with C4b binding protein (C4b-BP). The remaining 40% of PS is the activated Protein C cofactor.

Acquired Deficiency:
·DIC
·Severe Liver disease
·Vitamin K deficiency
·Oral anticoagulation therapy
·Pregnancy

Testing: Protein S can be measured by clot-based (functional), ELISA (Antigenic) or Agglutination. Total and Free Protein S antigen can be measured by agglutination or ELISA.

Congenital Deficiency:
Congenital Protein S deficiencies’ classification is based on the comparison of functional and antigenic (free and total).
Classification of congenital Protein S deficiency:

 
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