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 and normalized 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

Normalized APCR Ratio (NAPC):

≥1 year

0.83 - 1.12

Critical Values:



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


PTT performed on patient plasma with and without the addition of Activated Protein C. Ratio and normalized ratio comparing patient and normal are reported.


Fairview University Medical Center Web Page February 2014


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.

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