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Protein C Activity, Plasma

Measurement of plasma C protein activity is used to investigate patients with congenital or acquired C protein deficiency as well as in patients with a severe family history or in patients who have already experienced a thromboembolic episode.

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Activated protein C is found in plasma, is a glycoprotein dependent on vitamin K and acts as an anticoagulant by inhibiting coagulation factors V and XIII. Protein C was first identified in the early 1980s. 60% of protein C is bound to a complement protein and is converted to its activated functional form by the action of a protease, and its activity is enhanced by a cofactor, S protein.

Protein C deficiency can be congenital or acquired.

Congenital deficiency of protein C is an inherited, dominant type of autosomal thrombophilia, responsible for 3-5% of cases of venous thrombosis. Congenital deficiency can manifest either as reduced levels of protein C or as resistance to protein C, despite its normal levels. Patients with homozygous deficiencies usually die as a result of thrombosis during their first year of life. Patients with heterozygous protein C deficiency often have thromboembolic episodes of venous thrombosis, such as deep vein thrombosis or pulmonary embolism, at an early age.

Acquired protein C deficiency is observed in acute respiratory distress syndrome, diffuse intravascular coagulation, hemolytic uremic syndrome, liver disease, infection, postoperative conditions, and vitamin K deficiency. Protein deficiency is responsible for a much higher percentage of venous than arterial thrombosis. The factor V Leiden mutation is a molecular defect in factor V, making it resistant to anticoagulant activation by protein C. It is an important cause of deep vein thrombosis as this mutation occurs in 5% of the population.

Possible Interpretations of Pathological Values
  • Increase: Diabetes, nephrotic syndrome
  • Decrease: Acute consumption (as in diffuse intravascular coagulation), congenital protein C deficiency, liver disease, vitamin K deficiency Medications: Antibiotics, aparaginase, estrogen, warfarin




Important Note

Laboratory test results are the most important parameter for the diagnosis and monitoring of all pathological conditions. 70%-80% of diagnostic decisions are based on laboratory tests. Correct interpretation of laboratory results allows a doctor to distinguish "healthy" from "diseased".

Laboratory test results should not be interpreted from the numerical result of a single analysis. Test results should be interpreted in relation to each individual case and family history, clinical findings and the results of other laboratory tests and information. Your personal physician should explain the importance of your test results.

At Diagnostiki Athinon we answer any questions you may have about the test you perform in our laboratory and we contact your doctor to get the best possible medical care.


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