Protein C activity

Description: 
The BIOPHENTM Protein C liquid reagent technology (LRT) kit is a chromogenic method for the in vitro quantitative determination of Protein C activity in human citrated plasma. Protein C in plasma is activated by an enzyme purified from the venom of the Southern Copperhead snake (Agkistrodon C contortrix). The amount of activated protein C thus formed is determined by the rate of hydrolysis of the chromogenic substrate SaPC-21. The pNA released is measured at 405 nm and is proportional to the protein C level.
Clinical details: 
The complex orchestration of cellular and molecular participants of haemostasis achieves a crucial yet fine balance of procoagulant and anticoagulant mechanisms. Deficiencies of natural anticoagulant regulators of secondary haemostasis, such as antithrombin, protein C and protein S, and gain of function mutations in genes for FII and FV, are heritable disorders that can shift this balance and increase the risk of venous thromboembolic disease.Protein C (PC) is the vitamin K dependent zymogen of the serine protease activated protein C (APC), which functions as a regulator of secondary haemostasis by inactivating FVa & FVIIIa within a forming clot. PC attaches to vessel endothelium via a specific receptor, endothelial PC receptor (EPCR) and then migrates across the endothelial surface 'in search' of its activator. If a clot is being formed, some of the thrombin leaks onto the endothelial surface and encounters membrane-bound thrombomodulin (TM), whereupon they form a complex that induces a conformational change in thrombin such that it loses procoagulant activity and instead adopts an anticoagulant role by activating PC. The APC/EPCR complex then dissociates from the TM-throbmin complex and the APC is released to migrate onto the surface of an activated platelet. PC & its non-enzymatic cofactor protein S (PS) are vitamin K dependent and so bind to surface phospholipid and PS orientates the active site of PC above the platelet surface to facilitate inactivation of substrates by cleavage of a small number of peptide bonds. Inactivation of FVIIIa additionally requires zymogen FV to operate synergistically with PS in a cofactor role.

Deficiency of PC can be qualitative or quantitative and reduces the effectiveness of haemostasis regulation, thus tipping the balance towards an increased risk of venous thromboembolism.
Reference range: 

78-148 iu/dL

Synonyms or keywords: 
protein C activity, PC Act.
Units: 
iu/dL
Sample type and Volume required: 
External requests: Citrated platelet poor plasma (500µL x 1 aliquot)
Internal requests: please refer to EPIC label
Call in advance: 
Yes
Turnaround time: 
7 - 10 days
Special sample instructions: 

The sample should be analysed or processed & stored within 8 hours of venepuncture. Please ensure sample tubes are filled exactly to the fill-line as underfilling or overfilling creates a dilution error and leads to inaccurate results.

Storage and transport: 
It is advised that citrated plasma is frozen prior to transport and sent to the laboratory on dry ice to maintain sample quality and integrity. If whole blood citrate sample is sent, it is required to be sent at room temperature and must arrive to the laboratory within 8 hours of venepuncture.
Contacts:
Diagnostic Haemostasis and Thrombosis Department
St Thomas': 020 7188 2797; Guy's: 020 7188 7188 ext. 53860
St Thomas' Hospital
North Wing - 4th and 5th Floors
Westminster Bridge Road
London SE1 7EH

Laboratory opening times
24/7

Guy's Hospital
Southwark Wing - 4th Floor
Great Maze Pond
London SE1 9RT

Outside core hours, contact Duty Haemostasis Biomedical Scientist
For clinical advice or interpretation of results, please contact the laboratory in the first instance.

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Last updated: 04/10/2023