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Protein C, Functional

CPT: 85303
Updated on 11/23/2021
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Synonyms

  • Functional Protein C
  • Protein C Activity (Chromogenic)
  • Functional Protein C
  • <
  • Functional Protein C
  • Protein C Activity (Chromogenic)

Special Instructions

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.

If the patient's hematocrit exceeds 55%, the volume of citrate in the collection tube must be adjusted. Refer to Coagulation Collection Procedures for directions.


Expected Turnaround Time

2 - 3 days



Related Documents

For more information, please view the literature below.

Procedures for Hemostasis and Thrombosis: A Clinical Test Compendium


Specimen Requirements


Specimen

Plasma, frozen


Volume

1 mL


Container

Blue-top (sodium citrate) tube


Collection

Blood should be collected in a blue-top tube containing 3.2% buffered sodium citrate.1 Evacuated collection tubes must be filled to completion to ensure a proper blood-to-anticoagulant ratio.2,3 The sample should be mixed immediately by gentle inversion at least six times to ensure adequate mixing of the anticoagulant with the blood. A discard tube is not required prior to collection of coagulation samples, except when the sample is collected using a winged (ie, "butterfly") collection system. With a winged blood collection set a discard tube should be drawn first to account for the dead space of the tubing and prevent under-filling of the evacuated tube.4,5 When noncitrate tubes are collected for other tests, collect sterile and nonadditive (red-top) tubes prior to citrate (blue-top) tubes. Any tube containing an alternative anticoagulant should be collected after the blue-top tube. Gel-barrier tubes and serum tubes with clot initiators should also be collected after the citrate tubes.

Please print and use the Volume Guide for Coagulation Testing to ensure proper draw volume.


Storage Instructions

Freeze


Patient Preparation

Ideally, the patient should not be on anticoagulant therapy. Avoid warfarin (Coumadin®) therapy for two weeks prior to the test and heparin, direct Xa, and thrombin inhibitor therapies for about three days prior to testing. Do not draw from an arm with a heparin lock or heparinized catheter.


Causes for Rejection

Severe hemolysis; improper labeling; clotted specimen; specimen diluted with IV fluids; samples thawed in transit; improper sample type; sample out of stability


Test Details


Use

Confirmation and characterization of protein C deficiency


Limitations

Individuals with heterozygous PC deficiency may have low normal PC levels.6 Treatment with warfarin decreases the levels of vitamin K-dependent factors including PC. PC levels start to drop after six hours of warfarin treatment and do not regain pretreatment levels until generally two weeks after cessation of therapy. Elevated factor VIII levels, as can be seen in acute phase reaction, can normalize the aPTT and effectively reduce PC levels.7 PC levels can be falsely low in patients with the factor VLeiden mutation. PC levels can become depleted as the result of activation of coagulation limiting the utility of testing for congenital PC deficiency during the immediate convalescent period after a thrombotic event.6 Heparin therapy up to 1 unit/mL does not affect PC levels.6 This test should not be used for patients receiving thrombin inhibitors such as hirudin and argatroban.7


Methodology

Protein C in plasma is activated by a specific enzyme (protein C activator) from copperhead snake venom (Agkistrodon contortrix). The amount of activated protein C is determined. The resulting activated PC (Protein Ca) is determined as the rate of hydrolysis of a chromogenic substrate in a kinetic test by measuring the increase in absorbance at 405 nm.

A specific enzyme extracted from the venom of Agkistrodon c. contortrix is used to activate PC in the patient sample. All other factors required for normal aPTT are supplied in the reagent. The activated protein C inhibits factors V and VIII in the reagent and the resultant prolongation of the aPTT-based clotting time is proportional to plasma PC activity.

Protein C in plasma is activated by a specific enzyme (protein C activator) from copperhead snake venom (Agkistrodon contortrix). The amount of activated protein C is determined. The resulting activated PC (Protein Ca) is determined as the rate of hydrolysis of a chromogenic substrate in a kinetic test by measuring the increase in absorbance at 405 nm.


Additional Information

See Protein C Deficiency Profile [283655] for more clinical information.


Footnotes

1. Adcock DM, Kressin DC, Marlar RA. Effect of 3.2% vs 3.8% sodium citrate concentration on routine coagulation testing. Am J Clin Pathol. 1997 Jan; 107(1):105-110. 8980376
2. Reneke J, Etzell J, Leslie S, Ng VL, Gottfried EL. Prolonged prothrombin time and activated partial thromboplastin time due to underfilled specimen tubes with 109 mmol/L (3.2%) citrate anticoagulant. Am J Clin Pathol. 1998 Jun; 109(6):754-757. 9620035
3. National Committee for Clinical Laboratory Standardization. Collection, Transport, and Processing of Blood Specimens for Coagulation Testing and General Performance of Coagulation Assays; Approved Guideline. 5th ed. Villanova: NCCLS; 2008. Document H21-A5:28(5)
4. Gottfried EL, Adachi MM. Prothrombin time and activated partial thromboplastin time can be performed on the first tube. Am J Clin Pathol. 1997 Jun; 107(6):681-683. 9169665
5. McGlasson DL, More L, Best HA, Norris WL, Doe RH, Ray H. Drawing specimens for coagulation testing: Is a second tube necessary? Clin Lab Sci. 1999 May-Jun; 12(3):137-139. 10539100
6. Adcock DM, Bethel MA, Macy PA. Coagulation Handbook. Aurora, Colo: Esoterix−Colorado Coagulation; 2006.
7. Van Cott EM, Laposata M. Coagulation. In: Jacobs DS, DeMott WR, Oxley DK, eds. Laboratory Test Handbook With Key Word Index. Hudson, Ohio: Lexi-Comp; 2001:327-358.

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
117705 Protein C-Functional 27819-2 117705 Protein C-Functional % 27819-2

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