Protein C (PC) Chromogenic Assay

Coagulation

Description

Protein C (PC) is a vitamin K dependent glycoprotein synthesised in the liver. PC is activated by thrombin-thrombomodulin complex to ACTIVATED PROTEIN C (APC) which then destroys factors Va and VIIIa by limited proteolysis in the presence of protein S. Familial PC deficiency can be classified into two types, type I or II on the basis of phenotypic tests.

Protein C shares many features with the other vitamin K dependent factors (i.e. II, VII, IX, X and Protein S). Protein C is synthesised in the liver and requires vitamin K to complete the synthesis of the physiologically competent proenzyme.

Protein C activity is reduced in vitamin K deficiency and in the presence of oral anticoagulation by vitamin K antagonists such as warfarin. In anticoagulated patients, the Protein C antigen can be compared (by ratio) to antigen levels of two other vitamin K dependent clotting factors (usually factors VII and X) to indicate whether PC deficiency is likely or unlikely. However, guidelines recommend against measuring protein C in patients on vitamin K antagonists such as Warfarin because detection is not reliable.

Indications

As a part of the thrombophilia screen and may be requested to investigate 1st degree relatives of patients with protein C deficiency.

The rare Type 2B Protein C deficiencies will not be detected by chromogenic assays.

Sample Type

Plasma (Citrate Blue) x 1.

Reference Range

Reference range indicated on report.

Turnaround Time

Within 14 days

Testing Frequency

Weekly.

External Notes

Adult reference range reported, reduced levels may be present in teenagers, reduced levels in children and babies. Protein C antigen, factor X antigen and factor VII antigen will normally be performed on unexpected low protein C activity assay.

Patient Preparation

No special requirements.

References

Guidelines on the laboratory aspects of assays used in haemostasis and thrombosis Mackie I, P. Cooper, A. Lawrie, S. Kitchen, E. Gray, M. Laffan International journal of laboratory haematology. Volume 35, Issue 1, pages 1-13, February 2013
The phenotypic and genetic assessment of protein C deficiency. Cooper PC, Hill M, Maclean RM. Int J Lab Hematol. 2012 Aug;34
Baglin et al; British Committee for Standards in Haematology. Clinical guidelines for testing for heritable thrombophilia. Br J Haematol. 2010 Apr;149(2):209-220.

Your contact for this test

Kieron Hickey

Thrombophilia Section Lead and Deputy Laboratory Manager - Coagulation

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Protein C (PC) Chromogenic Assay