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HelpTest ID APCRR Activated Protein C Resistance V, with Reflex to Factor V Leiden, Blood and Plasma
Useful For
Evaluation of patients with incident or recurrent venous thromboembolism (VTE)
Evaluation of individuals with a family history of VTE
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| APCRV | Activated Protein Resistance V, P | Yes | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| F5DNA | Factor V Leiden (R506Q) Mutation, B | Yes | No |
| F5DNI | APCRV/F5DNA Summary Interpretation | No | No |
Testing Algorithm
If the assay ratio is abnormal, then R506Q mutation analysis will be performed at an additional charge.
When the activated protein C resistance V is abnormal or indeterminate and R506Q mutation assay is reflexed, then a summary interpretation will be provided.
Special Instructions
Method Name
Optical Clot-Based
Reporting Name
APCRV, w/Reflex, PSpecimen Type
Plasma Na CitWhole blood
Necessary Information
If priority specimen, mark request form, give reason, and request a call-back.
Specimen Required
See Coagulation Guidelines for Specimen Handling and Processing in Special Instructions.
Blood and plasma are required.
Specimen Type: Whole blood
Container/Tube:
Preferred: Yellow top (ACD)
Acceptable: Lavender top (EDTA) or light-blue top (3.2% sodium citrate)
Specimen Volume: Full tube
Collection Instructions:
1. Invert several times to mix blood.
2. Send specimen in original tube.
Additional Information: Each molecular coagulation test requested must have its own tube.
Specimen Type: Platelet-poor plasma
Patient Preparation: Fasting preferred
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Submission Container/Tube: Polypropylene vial
Specimen Volume: 1 mL
Collection Instructions:
1. Within 4 hours of collection, centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again. Aliquot plasma into separate plastic vial leaving 0.25 mL in the bottom of centrifuged vial.
2. Freeze plasma aliquot immediately at -20° C, or, ideally ≤-40 degrees C.
Additional Information:
1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
2. Each coagulation assay requested should have its own vial.
Specimen Minimum Volume
Plasma: 0.5 mL
Whole Blood: 3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Na Cit | Frozen | 14 days | |
| Whole blood | Ambient (preferred) | 7 days | |
| Frozen | 14 days | ||
| Refrigerated | 14 days |
Clinical Information
Protein C, a part of the natural anticoagulant system, is a vitamin K-dependent protein zymogen (molecular weight=62,000 da) that is synthesized in the liver and circulates at a plasma concentration of approximately 5 mcg/mL. Protein C is activated to activated protein C (APC) via proteolytic cleavage by thrombin bound to thrombomodulin, an endothelial cell surface membrane protein. APC downregulates the procoagulant system by proteolytically inactivating procoagulant factors Va and VIIIa. Protein S, another vitamin K-dependent coagulation protein, catalyzes APC inactivation of factors Va and VIIIa. APC interacts with and proteolyses factors V/Va and VIII/VIIIa at specific APC binding and cleavage sites, respectively. Resistance to activated protein C (APC resistance) is a term used to describe abnormal resistance of human plasma to the anticoagulant effects of human APC. APC resistance is characterized by a reduced anticoagulant response of patient plasma after adding a standard amount of APC. For this assay, the activated partial thromboplastin time clotting test fails to prolong significantly after the addition of APC.
The vast majority of individuals with familial APC resistance have a specific point mutation in the procoagulant factor V gene (1691G>A, factor V Leiden) encoding for a glutamine (Q) substitution for arginine (R)-506 in the heavy chain of factor V (factor V R506Q). This amino acid change alters an APC cleavage site on factor V such that factor V/Va is partially resistant to inactivation by APC. The carrier frequency for the factor V Leiden mutation varies depending on the population. Approximately 5% of asymptomatic white Americans of non-Hispanic ancestry are heterozygous carriers, while the carrier frequency among African Americans, Asian Americans, and Native Americans is less than 1%, and the carrier frequency for Hispanics is intermediate (2.5%). The carrier frequency can be especially high (up to 14%) among whites of Northern European or Scandinavian ancestry. Homozygosity for factor V Leiden is much less common, but may confer a substantially increased risk for thrombosis. The degree of abnormality of the APC-resistance assay correlates with heterozygosity or homozygosity for the factor V Leiden mutation; homozygous carriers have a very low APC-resistance ratio (eg, 1.1-1.4), while the ratio for heterozygous carriers is usually 1.5 to 1.8.
Reference Values
APCRV RATIO
≥2.3
Pediatric reference range has neither been established nor is available in scientific literature. The adult reference range likely would be applicable to children older than 6 months.
Interpretation
An activated protein C (APC) resistance ratio below 2.3 suggests abnormal resistance to APC of hereditary origin.
If the screening APC resistance test is abnormal, DNA-based testing for the factor V Leiden mutation factor V Leiden (R506Q) mutation is performed to confirm or exclude hereditary APC-resistance.
Clinical Reference
1. Nichols WL, Heit JA: Activated protein C resistance and thrombosis. Mayo Clin Proc 1996;71:897-898
2. Dahlback B: Resistance to activated protein C as risk factor for thrombosis: molecular mechanisms, laboratory investigation, and clinical management. Semin Hematol 1997;34(3):217-234
3. Rodeghiero F, Tosetto A: Activated protein C resistance and Factor V Leiden mutation are independent risk factors for venous thromboembolism. Ann Intern Med 1999;130:643-650
4. Grody WW, Griffin JH, Taylor AK, et al: American College of Medical Genetics consensus statement on factor V Leiden mutation testing. Genet Med 2001;3:139-148
5. Press RD, Bauer KA, Kujovich JL, Heit JA: Clinical utility of factor V Leiden (R506Q) testing for the diagnosis and management of thromboembolic disorders. Arch Pathol Lab Med 2002;126:1304-1318
6. Yohe S, Olson J. Chapter 38: Thrombophilia: Assays and Interpretation. In Laboratory Hematology Practice. Edited by K Kottke-Marchant. Wiley Blackwell Publishing. 2012. pp 492-508
Day(s) and Time(s) Performed
Monday through Friday
Analytic Time
4-7 daysCPT Code Information
85307
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| APCRR | APCRV, w/Reflex, P | 13590-5 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| APCR | APCRV Ratio | 13590-5 |
| INT55 | Interpretation | 48591-2 |
Forms
1. New York Clients-Informed consent is required. Document on the request form or electronic order that a copy is on file. The following documents are available in Special Instructions:
-Informed Consent for Genetic Testing (T576)
-Informed Consent for Genetic Testing-Spanish (T826)
2. Coagulation Patient Information (T675) in Special Instructions
3. If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.