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Test Code LAB489 Protein C Activity

Clinical Information

Used to identify and quantitate a Protein C defect or deficiency in those patients subject to recurrent venous thrombosis or pulmonary emboli.

Synonym

  • PROTC
  • Protein C Functional
  • PC Functional
  • PC Activity

Specimen Required

Preferred Container/Tube: 3.2% Citrate Blue Top - 2.7 mL
Specimen Volume: 2.7 mL
Acceptable Container/Tube: 3.2% Citrate Blue Top - 1.8 mL
Specimen Volume: 1.8 mL
Platelet poor plasma (PPP):
Specimen Volume: 2 - 1 mL aliquots platelet poor plasma (PPP)
Specimen Minimum Volume: 1 - 1 mL aliquot platelet poor plasma (PPP)

Specimen Collection Information

For Outreach, other than OSU Patient Service Centers: Samples must be processed and received frozen/must remain frozen in transit. 

For sending frozen plasma specimens, process immediately upon receipt. Centrifuge capped specimen tube in accordance with CLSI H21, at a speed and time required to consistently produce platelet-poor plasma (PPP = platelet count <10 K/uL). Transfer PPP into plastic aliquot tubes, cap and freeze. DO NOT transport until specimens are completely frozen.

Specimen Stability Information

Ambient: 
     Whole blood: 1 hour
      Platelet poor plasma: 4 hours
Frozen: 
      Platelet poor plasma: PPP removed from the cells and frozen at -20°C or ideally -70°C.

Rejected Due To

  • Ambient WB specimens >1 hour old
  • Ambient PPP specimens >4 hours old
  • Clotted specimens
  • Underfilled or overfilled tube
  • Hemolysis

Reference Values

0-4 days: 17-53 % Activity
5-29 days: 20-64 % Activity
30-89 days: 21-65 % Activity
90-179 days: 28-80 % Activity
180-365 days: 37-81 % Activity
1-5 years: 56-150 % Activity
6-10 years: 40-92 % Activity
11-16 years: 55-111 % Activity
17+ years: 72-220 % Activity

Interpretation

Test results are reported in P2Y12 Reaction Units (PRU). The pre-drug Normal Reference Range is 194 - 418 PRU. PRU measures the extent of platelet aggregation in the presence of P2Y12 inhibitor drugs such as clopidogrel (Plavix), prasugrel (Effient), ticlopidine (Ticlid), and ticagrelor (Brilinta). 

Cautions

This test is not indicated in patients receiving Coumadin (warfarin) therapy. This test is not indicated for inpatient evaluation of acute thrombosis.

Method Description

This clotting assay measures Protein C which is activated in the presence of the specific activator extracted from Agkistrodon c. contortrix venom. The resulting activated protein C inhibits the factors V and VIII, and thus prolongs the APTT of a system in which all the factors are present, constant and in excess (provided by the test system), except for the protein C which is derived from the sample being tested.

Performing Lab

Clinical Lab UH

Day(s) Performed

Monday through Friday (excludes OSU holidays)

Report Available

Same day/1 day

Reporting Name

Protein C Activity

CPT Code Information

85303

LOINC Code Information

27819-2