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HelpTest Code F_7 Coagulation Factor VII Activity Assay, Plasma
Reporting Name
Coag Factor VII Assay, PUseful For
Diagnosing congenital deficiency of coagulation factor VII
Evaluating acquired deficiencies associated with liver disease, oral anticoagulant therapy, and vitamin K deficiency
Determining degree of anticoagulation with warfarin to correlate with level of protein C
Investigation of a prolonged prothrombin 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, we suggest ordering Coagulation Consultations.
Necessary Information
If priority specimen, mark request form, give reason, and request a call-back.
Specimen Required
Specimen Type: Platelet-poor plasma
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)
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
Adults: 65-180%
Normal, full-term newborn infants or healthy premature infants may have decreased levels (≥20%) which increase within the first postnatal week but may not reach adult levels for ≥180 days postnatal.*
*See Pediatric Hemostasis References section in Coagulation Guidelines for Specimen Handling and Processing
Day(s) Performed
Monday through Saturday
CPT Code Information
85230
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| F_7 | Coag Factor VII Assay, P | 3198-9 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| F_7 | Coag Factor VII Assay, P | 3198-9 |
Clinical Information
Factor VII is a vitamin K-dependent serine protease synthesized in the liver. It is a component of the extrinsic coagulation scheme, measured by the prothrombin time. Plasma biological half-life is about 3 to 6 hours. Deficiency may result in a bleeding diathesis.
Interpretation
Liver disease, vitamin K deficiency, or warfarin anticoagulation can cause decreased factor VII activity.
Newborn infants usually have levels 25% or more.
Cautions
Factor VII is the first vitamin K-dependent coagulation factor to decrease after starting warfarin therapy and one of the first to return to normal when anticoagulation is discontinued.
Method Description
The factor VII 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 VII-deficient substrate (normal plasma depleted of factor VII 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)