Activated Protein C Resistance

APC Resistance, APCR

Test Codes

EPIC: LAB1231059

Department

Coagulation

Instructions

Specimens with hematocrit values greater than 55% must have anticoagulant adjusted. Specimens must be re-collected using a specified whole blood to sodium citrate ratio. Contact the performing Laboratory for specific instructions.

Specimen Collection Criteria

Collect: One Light Blue-top 3.2% Sodium Citrate tube.

TUBE MUST BE FULL. 

Greiner brand tubes must be filled to the black arrow.

Physician Office/Draw Specimen Preparation

For optimal results, maintain whole blood specimen at room temperature (20-26°C or 68-78.8°F) prior to transport. Transport whole blood to the Laboratory within 4 hours of collection. If transport within 4 hours is not possible, the following procedure must be followed for accurate results:

1. Centrifuge the capped tubes at 1500 x g for 15 minutes.
2. Transfer plasma with plastic pipette into a plastic polypropylene centrifuge tube, cap and centrifuge an additional 15 minutes at 1500 x g to obtain platelet poor plasma (PPP) which has a platelet count less than 10 bil/L. Plasma with a platelet count of less than 10 bil/L is critical for accurate results.
3. Immediately remove only the top two-thirds of the PPP and transfer into a screw cap, 5 ml, 75 x 13 mm, round base, tube.
4. Freeze (-20°C/-4°F or below) the PPP immediately.

5. Transport frozen on DRY ICE. Specimen must remain frozen during transport.

Preparation for Courier Transport

Transport: Whole blood at room temperature (20-26°C or 68-78.8°F), or plasma obtained through the process listed above, frozen (-20°C/-4°F or below).

Rejection Criteria

• Glass tubes and 3.8% Sodium Citrate tubes.
• Specimens that are clotted or grossly hemolyzed.
• Inappropriate specimen volume.
• Thawed or partially thawed specimens.

In-Lab Processing

Whole blood specimens must be processed as follows upon receipt in the Laboratory: 

1. Centrifuge the capped tubes at 1500 x g for 15 minutes.
2. Transfer plasma with plastic pipette into a plastic polypropylene centrifuge tube, cap and centrifuge an additional 15 minutes at 1500 x g to obtain platelet poor plasma (PPP) which has a platelet count less than 10 bil/L. Plasma with a platelet count of less than 10 bil/L is critical for accurate results.
3. Immediately remove only the top two-thirds of the PPP and transfer into a plastic tube.

4. Test or freeze specimen according to lab protocol. 

 

Storage

Specimen Stability for Testing:

Whole Blood
Room Temperature (20-26°C or 68-78.8°F): 4 hours
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): Unacceptable

Platelet Poor Plasma (PPP)
Room Temperature (20-26°C or 68-78.8°F): Unacceptable
Refrigerated (2-8°C or 36-46°F): Unacceptable
Frozen (-20°C/-4°F or below): 30 days

Specimen Storage in Department Prior to Disposal:

Frozen (-20°C/-4°F or below): 30 days

Laboratory

Royal Oak Coagulation Laboratory

Performed

Minimum once per week. 
Results are available within 7-10 days.

Reference Range

Normal: Greater than or equal to 2.3.

Test Methodology

Change in Optical Density (IL ACL TOP Series).

Interpretation

• Multiple different mutations in the factor V gene can result in activated protein C resistance (APCR). In more than 90% of cases of APCR, there is a mutation in factor V gene (FV Leiden). This results in the FV gene making the protein resistant to inactivation by Activated Protein C (APC), thus creating higher risk of thrombosis.
• Interferences: Initial oral anticoagulant treatment before stabilization and levels of Protein C below 50% may give low APCR ratios.

Clinical Utility

Activated protein C resistance results in an increased risk of thrombosis, and therefore, can be useful in investigation of venous thromboembolism. 

CPT Codes

85307

LOINC: 13590-5

Contacts

Last Updated

8/13/2025