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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Protein C Activity

Test Code(s): PC-ACT / XPCF

CPT Code(s): 85303

Methodology: Chromogenic Assay

Clinical Significance: Test is used for the qualitative determination of plasma
Protein C activity by chromogenic method.

Days Performed: Mon-Fri, dayshift - day varies. Specimens are accepted at any time. Testing required during off hours must be approved by a Coagulation physician. Call 263-5005 before collection.

Turnaround Time: Stat: 1 working day.
Routine: 7 - 10 working days.

Specimen Requirements

Specimen: Blood

Patient Preparation: The assay is more accurate in the measurement of Protein C in
patients taking warfarin, dabigatran, rivaroxaban, edoxaban,

Collection Instructions: Do NOT draw through a line containing heparin. The
venipuncture MUST be atraumatic to avoid hemolysis and
contamination with tissue factors and platelets. Tube must
be allowed to fill completely.  

Indicate if patient is receiving anticoagulant
(warfarin/Heparin/Vitamin K antagonist), direct thrombin
inhibitor or fibrinolytic agent therapy.

Collection Container: Preferred: Light blue top (3.2% NaCitrate)

Collection Volume: Preferred: Full 3.5 mL tube
Pediatrics: Pediatric tube filled to fill mark

Sample Analyzed: Plasma

Volume Required: Preferred: 1.5 mL
Pediatrics: 0.5 mL

Specimen Processing: Centrifuge specimen to yield platelet poor plasma (platelet
count should be less than 10 K/uL). Separate plasma and
transfer to plastic tube or vial. Freeze plasma within 4 hours
of collection at -20C or below.  

Specimen Transport: Transport whole blood specimen at room temperature to UWHC
Laboratory (B4/220) within 4 hours of collection. See
Processing for instructions if transport criteria are not
Transport frozen plasma aliquot on dry ice to UWHC Core
Laboratory (B4/220).

Outreach Specimen Transport: Centrifuge specimen to yield platelet poor plasma (platelet
count should be 10 K/µL or less). Separate plasma and
transfer to labeled plastic tube and spin again. Transfer
plasma from second spin to clean plastic labeled tube or
vial. Indicate on tube "spun twice". Freeze plasma within 4
hours of collection at -20°C or below.

Unacceptable Criteria: Hemolyzed specimens, clotted specimens, partially filled tubes
and whole blood specimens greater than 4 hours old when
received by the laboratory are not acceptable.

Stability: Ambient: 4 hours on spun tube
Refrigerated: Not acceptable
Frozen: 1 month at -20C; 6 months at -70C


Reference Interval:

17 years and up: 70-160 %NPP



At birth, Protein C levels are only about 35% of adult normal values on average. Mean Protein C levels rise to above 50% of adult normal values by age 6 months, but may remain below adult normal range until the age of 10-16 years of age.

Protein C Activity

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