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HelpTest Code FACTV Coagulation Factor V Activity Assay, Plasma
Reporting Name
Coag Factor V Assay, PUseful For
Diagnosing congenital deficiencies (rare) of coagulation factor V
Evaluating acquired deficiencies associated with liver disease, factor V inhibitors, myeloproliferative disorders, and intravascular coagulation and fibrinolysis
Investigation of prolonged prothrombin time or activated partial thromboplastin time
Method Name
Optical Clot-Based
Performing Laboratory
Mayo Clinic Laboratories in Rochester
Specimen Type
Plasma Na CitOrdering Guidance
Coagulation testing is highly complex, often requiring the performance of multiple assays and correlation with clinical information. For that reason, consider ordering a Coagulation Consultation.
Necessary Information
If priority specimen, mark request form, give reason, and request a call-back.
Specimen Required
Patient Preparation: Patient must not be receiving coumadin (warfarin) or heparin therapy. (If not possible for medical reasons, note on request.)
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Submission Container/Tube: Plastic vial
Specimen Volume: 1 mL
Collection Instructions:
1. Specimen must be collected prior to factor replacement therapy.
2. For complete instructions, see Coagulation Guidelines for Specimen Handling and Processing
3. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.
4. Aliquot plasma into a plastic vial, leaving 0.25 mL in the bottom of centrifuged vial.
5. Freeze plasma immediately (no longer than 4 hours after collection) at -20° C or, ideally, -40° C or below.
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
0.5 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Plasma Na Cit | Frozen | 14 days |
Reject Due To
| Gross hemolysis | Reject |
| Gross lipemia | Reject |
| Gross icterus | Reject |
Special Instructions
Reference Values
>1 month: 70%-165%
<1 month: Normal, full-term and premature newborn infants may have mildly decreased levels (≥30% to 35%) which reach adult levels within 21 days postnatal.
*See Pediatric Hemostasis References section in Coagulation Guidelines for Specimen Handling and Processing
Day(s) Performed
Monday through Saturday
CPT Code Information
85220
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| FACTV | Coag Factor V Assay, P | 3193-0 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| FACTV | Coag Factor V Assay, P | 3193-0 |
Clinical Information
Factor V is a vitamin K-independent protein synthesized in the liver and in other tissues (endothelium, megakaryocytes/platelets). In its thrombin-activated form (factor Va), it serves as an essential cofactor in the prothrombinase enzyme complex, which converts prothrombin to thrombin (the prothrombinase complex consists of the enzyme, activated factor X, factor Va cofactor, a phospholipid surface, and calcium).
Deficiency of factor V may cause prolonged prothrombin time and activated partial thromboplastin time and may result in a bleeding diathesis. Plasma biological half-life varies from 12 to 36 hours.
Platelets contain 20% to 25% of the factor V in blood. Factor V (also known as labile factor) is highly susceptible to proteolytic inactivation, with the potential for spuriously decreased assay results.
Interpretation
Acquired deficiencies are much more common than congenital.
Patients that are congenitally deficient homozygous generally have activity levels less than or equal to10% to 20%.
Patients that are congenitally deficient heterozygous generally have activity levels less than or equal to 50%.
Congenital deficiency may occur in combined association with factor VIII deficiency.
Cautions
Factor V (labile factor) is highly susceptible to proteolytic inactivation, with the potential for spuriously decreased assay results. In normal individuals, after freeze-thaw of citrate plasma, factor V activity typically may be 10% to 20% less than observed in a fresh plasma specimen, and in occasional individuals, a more marked decrease of factor V activity occurs. Normal results can be regarded as reliable, but decreased factor V activity results need to be correlated with other clinical and laboratory information. Repeat testing may be necessary.
Method Description
The factor V assay is performed on the Instrumentation Laboratory ACL TOP using the prothrombin time (PT) method and a factor-deficient substrate. Patient plasma is combined and incubated with a factor V-deficient substrate (normal plasma depleted of factor V by immunoadsorption). After a specified incubation time, a PT reagent is added to trigger the coagulation process in the mixture. Then the time to clot formation is measured optically at a wavelength of 671 nm.(Owen CA Jr, Bowie EJW, Thompson JH Jr: Diagnosis of Bleeding Disorders. 2nd ed. Little, Brown and Company; 1975; Meijer P, Verbruggen HW, Spannagi M: Clotting factors and inhibitors: Assays and interpretation. In: Kottke-Marchant K, ed. Laboratory Hematology Practice. Wiley Blackwell Publishing; 2012:435-446)