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UW Health SMPH
American Family Children's Hospital

UW Hospital and Clinics Lab Test Directory

Test Name: Activated Protein C Resistance

Test Code(s): APC-R / XAPCR

CPT Code(s): 85307

Test Description: Test Component:

Ratio of two APTT-based assays, one with activated protein C added.


Methodology: Mechanical Clot Detection

Clinical Significance: Screening test used as a predictor of the Factor V Leiden gene mutation, factor V:Q506 mutation.

Days Performed: Mon-Fri, dayshift - day varies.

Turnaround Time: Stat: Not available stat.
Routine: 7 - 10 working days.

Specimen Requirements

Specimen: Blood

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

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

Collection Volume: Preferred: Two full 3.5 mL tubes
Pediatrics: Pediatric tube filled to fill mark

Sample Analyzed: Plasma

Volume Required: Preferred: 1 mL
Pediatrics: 0.5 mL

Specimen Processing: KEEP ONE TUBE UNOPENED AND UNSPUN at room temperature. Centrifuge the other tube to obtain platelet poor plasma (platelet count should be less than 10 K/L). Separate plasma from cells and transfer to plastic vial. Freeze plasma at -20C or below.

Specimen Transport: Transport unopened tubes at room temperature to UWHC Core Laboratory (B4/220) within 4 hours of collection.  Otherwise, transport one unopened tube at room temperature and a frozen plasma aliquot on dry ice.

Unacceptable Criteria: Hemolyzed or clotted specimens are not acceptable. A partially filled tube is not acceptable. Activated Protein C Resistance cannot be done on patients with a Lupus Anticoagulant. Alternatively, Factor V Leiden Gene Mutation is available.

Stability: Ambient: 4 hours on spun tube
Refrigerated: Not acceptable
Frozen: Plasma:2 weeks at -20C; 6 months at -70C. Whole Blood: Not acceptable


Reference Interval:

Age 12 months and up: Ratio greater than or equal to 2.1 is negative for APC resistance. 

Test Limitations:

This method uses Factor V deficient plasma; therefore, APC resistance due to a mutation other than a Factor V Leiden will not be detected. Extreme Factor V activity deficiency and a presence of lupus anticoagulant may cause an erroneous result.

Additional Information:

This is NOT the assay for Protein C Activity or C Reactive Protein.

Protein C Resistance APC Resistance

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