Clinics and Departments

Laboratory Services

Lab Dept:


Test Name:


General Information

Lab Order Codes:



APC Cofactor; APC Resistance; APC Sensitivity; APC-R

CPT Codes:

85307 – Activated Protein C (APC) resistance assay

Test Includes:

APCR ratio


Test Indications:

Functional clotting test for resistance to activated Protein C. Up to 90% of activated Protein C resistance is caused by Factor 5 Leiden mutation which can be detected using PCR molecular testing.

●If APCR is positive (or borderline), Factor 5 Leiden mutation is recommended.
●If APCR is positive and Factor 5 Leiden is negative, APCR is likely due to another mutation (10-15% of cases).
●If APCR is negative, it is unlikely any Factor 5 mutation is present.

Lab Testing Section:

Coagulation - Sendouts

Referred to:

Fairview University Medical Center

Phone Numbers:

MIN Lab: 612-813-6280

STP Lab: 651-220-6550

Test Availability:

Specimen is accepted and processed 24 hours/day, 7 days/week. Test is performed 1-2 times a week.

Turnaround Time:

Within 7 days

Special Instructions:

Test CAN be performed on patients on coumadin and/or heparin. Test CANNOT be performed on patients on argatroban or like products.


Specimen Type:

Whole blood


Light Blue top tube (Buffered Na citrate 3.2%)

Draw Volume:

2.7 mL (Minimum: 1.8 mL) blood

Processed Volume:

Specimens will be processed at reference lab facility if received within 4 hours of collection. Otherwise, specimens need to be processed at referring facility and provide minimum of two 0.5 mL specimens frozen at -70. Follow directions below under Special Processing.


Patients with hematocrit levels >55% must have a special tube made to adjust for the hematocrit, contact laboratory for special tube.

Special Processing:

Lab Staff: Do Not centrifuge. Do Not freeze. Send to reference lab in original Vacutainer® at room temperature if within 4 hours of collection. Forward promptly.

If specimen is >4 hours old prior to shipment, process specimen as follows:
Spin sample collected in blue top tube(s) for 5 minutes on the Stat Spin centrifuge, remove plasma and transfer to a 4 mL BCS sample cup(s), spin remaining plasma again for 5 minutes in the Stat Spin Centrifuge. Transfer plasma into two labeled 10x75 mL plastic tubes with a minimum of 0.5 mL in each. Freeze at -70 and send specimens on dry ice to Fairview University.

Patient Preparation:

Patient should not have received anticoagulants for 10-14 days prior to collection.

Sample Rejection:

Improper tube; clotted samples; underfilled tubes; overfilled tubes; samples from patients on Coumadin® or heparin


Reference Range:




APCR Ratio (ACR):

≥1 year

2.00 - 3.50

Critical Values:



Test CANNOT be performed on patients on argatroban or like products.


PTT’s on patient and normal plasma containing Factor 5 deficient plasma with and without addition of Activated Protein C (APC) Ratio is reported.


Fairview University Medical Center Web Page


6/2/2004: Test volume increased from 4.5 mL to 5.4 mL of blood.
5/3/2006: Reference ranges changed. Previously listed as APCR >1 year:1.57 - 2.72 and NAPR >1 year: 0.86 - 1.37
5/24/2010: Tubing patient specimens is no longer prohibited.
2/25/2014: Fairview specimen processing update.
8/6/2014: Normalized ratio is no longer reported with this test.

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