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protein S activity in plasma (protein S assay)

Indications: - hypercoagulability without other explanation - not routinely indicated in hypercoagulability workup Specimen: 1) plasma (citrate) 2) stable at room temperature for 8 hours 3) stable at -20 degrees C for 1 month Reference values: 1) total protein S: a) 70-140% of normal reference activity b) 0.67-1.25 U/mL c) 21-42 ug/mL 2) free protein S (active form) a) 60-120% of normal reference activity b) 0.23-0.49 U/mL Methods: 1) functional* clotting assay based on anticoagulant activity 2) rocket immunoelectrophoresis 3) enzyme-linked immunosorbant assays (ELISA) 4) microlatex particle mediated * NOT useful if patient is anticoagulated Increases: 1) pharmaceutical agents: - chemical interferences - heparin, warfarin 2) clinical disorders Decreases: 1) pharmaceutical agents - in vivo effects - oral contraceptives, L-asparaginase 2) clinical disorders: hypercoagulability a) congenital Protein S deficiency 1] low functional & antigenic levels 2] low functional & normal antigenic levels b) acquired Protein S deficiency - liver disease - increases in C4-binding protein may result in increased binding of protein S & decreased levels of free (active) protein S - inflammatory syndromes - estrogens, pregnancy - acute thrombosis - vitamin K deficiency, warfarin therapy - protein losing enteropathy c) only very low levels of plasma protein S (homozygous gene deletion) are associated with hypercoagulability

Related

free protein S in plasma protein S antigen in plasma protein S deficiency protein S; vitamin K-dependent protein S (PROS1, PROS)

General

clinical hematology test

References

  1. Medical Knowledge Self Assessment Program (MKSAP) 11, 16, 17, 18. American College of Physicians, Philadelphia 1998, 2012, 2015, 2018.
  2. Clinical Guide to Laboratory Tests, 3rd ed. Teitz ed., W.B. Saunders, 1995
  3. Protein S Functional Laboratory Test Directory ARUP: 30114
  4. Mini Panel of 2 tests: Protein C Functional . Protein S Functional Laboratory Test Directory ARUP: 30182
  5. Pintao MC et al. Protein S levels and the risk of venous thrombosis: Results from the MEGA case-control study. Blood 2013 Oct 31; 122:3210 PMID: 24014240 http://bloodjournal.hematologylibrary.org/content/122/18/3210