Questions and Answers
What is the role of activated protein C in the clotting assay described?
Inhibits factor V and factor VIII
How is the clotting time related to the percentage of protein C activity in the plasma dilution?
Inversely proportional
In the protein S antigen assay, what occurs when anti-protein S peroxidase conjugate is added?
Forms a sandwich with the free antigenic determinants of protein S
What is the effect of protein C activation in the presence of Protein C activator?
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What binds to the free antigenic determinants of protein S during the assay?
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How does the presence of activated protein C impact factor V and factor VIII?
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What is released from the substrate when a substrate is added to a plasma streptokinase mixture?
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What forms a plasminogen-streptokinase complex in the plasma specimen?
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How is the release of paranitroanilide (pNA) measured?
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What is the value of the pNA product directly proportional to?
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What catalyzes the release of paranitroanilide (pNA) from the substrate in the protein C chromogenic method?
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What reagent is typically added to stop the reaction in clotting time activity assays?
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What is the purpose of the Protamine Sulfate Dilution Test?
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What is the principle behind the Ethanol Gelation Test?
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Which of the following is a specific evidence of intravascular fibrin formation?
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In the laboratory profile of disseminated intravascular coagulation (DIC), which of the following is typically observed?
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Which of the following conditions is associated with a decreased level of plasminogen?
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Which of the following assays is based on the principle of agglutination of latex particles coated with antibodies against fibrin or fibrinogen fragments?
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What is the role of the enzyme peroxidase in the assay for Protein S?
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What percentage of total Protein S antigen in plasma is normally bound to C4b binding protein (C4b BP)?
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What is the role of free Protein S in the coagulation process?
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How is the Protein S bound to C4b BP removed from plasma in the assay?
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Which of the following conditions is NOT associated with an acquired deficiency of Protein S?
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What principle is used in the Protein S clotting assay to determine the percentage of functional Protein S?
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Study Notes
Protein C Clotting Assay
- Diluted plasma is incubated with protein C deficient plasma in the presence of protein C activator (Agkistrodon contortrix)
- The amount of protein C in plasma is related to the degree of correction obtained
- Activated protein C inhibits factor V and factor VIII (labile factors), causing prolongation of aPTT
- Clotting time obtained for each plasma dilution is inversely proportional to the percentage of protein C activity
Protein S Assay
- Plasma dilutions containing protein S antigen are incubated in microwells coated with anti-protein S antibody
- Anti-protein S peroxidase conjugate is added, binding to free antigenic determinants
- Plasminogen present in the plasma specimen forms a plasminogen-streptokinase complex, which possesses plasmin-like activity
- When a substrate is added, this plasmin-like activity releases pNA, which is measured spectrophotometrically
- The value of this product is directly proportional to the amount of plasminogen present in the plasma
Protein C Chromogenic Method
- Plasma is incubated with protein C activator (lyophilized powder from Agkistrodon contortrix venom)
- Upon addition of the substrate, activated protein C catalyzes the release of pNA from the substrate
- This is measured spectrophotometrically and is directly proportional to the concentration of protein C in the plasma
Disorders and Tests
- Disseminated Intravascular Coagulation (DIC)
- Laboratory profile:
- Platelet count
- Protime
- D-dimer
- Fibrinogen
- Laboratory profile:
- Tests for DIC:
- Protamine Sulfate Dilution Test
- Ethanol Gelation Test
- Latex Fibrin Degradation Product (FDP) Assay
- Latex D-Dimer Assay
- Plasminogen assay
- Measured by electro immunoassay and radioimmunoassay (RIA)
- Functional assays include fibrin plate and chromogenic assays
Protein S
- Free protein S component is a cofactor for the anticoagulant effects of activated protein C
- Protein S bound to C4b BP is removed from the plasma by precipitating with polyethylene glycol
- Acquired deficiencies of protein S:
- Using oral contraceptives
- Pregnancies
- Intake of oral anticoagulants
- DIC
- Liver disease
- Diabetes type I
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