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HelpTest ID 7INHE Factor VII Inhibitor Evaluation, Plasma
Ordering Guidance
This test is for factor VII inhibitors only. If the presence or type of inhibitor is unknown, order APROL / Prolonged Clot Time Profile, Plasma first, except for screening studies in patients with known hemophilia A or B.
Shipping Instructions
Send all vials in the same shipping container.
Necessary Information
If priority specimen, mark request form, give reason, and request a call-back.
Specimen Required
Patient Preparation:
1. Patient must not be receiving Coumadin (warfarin) or heparin therapy.
2. Fasting preferred
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (3.2% sodium citrate)
Submission Container/Tube: Plastic vial
Specimen Volume: 3 mL in 3 plastic vials, each containing 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 in Special Instructions.
3. Centrifuge, transfer all plasma into a plastic vial, and centrifuge plasma again.
4. Aliquot plasma (1-2 mL per aliquot) into 3 separate plastic vials 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.
 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.
Useful For
Detection and quantitation of inhibitor to coagulation factor VII
This test is not useful for the detection of a lupus-like circulating anticoagulant inhibitor, a nonspecific circulating anticoagulant, or other inhibitors that are not specific for coagulation factors.
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| 7INHT | FVII Inhib Profile Tech Interp | No | Yes |
| F_7 | Coag Factor VII Assay, P | Yes | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| 7AINH | FVII Inhib Profile Prof Interp | No | No |
| F7_IS | Factor VII Inhib Scrn | No | No |
| GBETH | General Factor Bethesda Units, P | No | No |
Testing Algorithm
Testing begins with coagulation factor VII activity assay with dilutions to evaluate assay inhibition; if the factor VII activity assay is normal or increased, a technical interpretation will be provided. If the factor VII activity assay is decreased, an inhibitor screen will be performed at an additional charge to look for specific factor VII inhibition and a professional interpretation will be provided. If specific inhibition is apparent, the titer of the inhibitor will be determined.
Special Instructions
Method Name
Optical Clot-Based
Reporting Name
Factor VII Inhib Profile, PSpecimen Type
Plasma Na CitSpecimen Minimum Volume
2 mL in 2 plastic vials, 1 mL each
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 |
Clinical Information
Coagulation factor inhibitors arise in patients who are congenitally deficient in a specific factor in response to factor replacement therapy, or can occur spontaneously without known cause or in response to a variety of medical conditions including the postpartum state, immunologic disorders, certain antibiotic therapies, some malignancies, and old age.
Inhibitors of factor VIII coagulant activity are the most commonly occurring of the specific factor inhibitors.
Reference Values
FACTOR VII ACTIVITY ASSAY
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 in Coagulation Guidelines for Specimen Handling and Processing in Special Instructions.
Interpretation
Normally, there is no inhibitor, ie, negative result.
If the screening assays indicate the presence of an inhibitor, it will be quantitated and reported in Bethesda (or equivalent) units.
Cautions
Occasionally, a potent lupus-like anticoagulant may cause false-positive testing for a specific factor inhibitor (eg, factor VIII or IX); see Ordering Guidance.
Clinical Reference
1. Hematology: Basic Principles and Practice. Seventh Edition. Edited by R Hoffman, EJ Benz Jr, LE Silberstein, et al. Elsevier, 2018
2. Kasper CK: Treatment of factor VIII inhibitors. Prog Hemost Thromb 1989;9:57-86
3. Laboratory Hematology Practice. Edited by K Kottke-Marchant. Wiley Blackwell Publishing, 2012
Method Description
Screening for inhibitors of specific coagulation factors is represented by the inhibitor assay for factor VII. This assay consists of measuring the difference in factor VII activity (prothrombin time based assay) before and after incubation of a mixture of normal plasma and patient's plasma for 1 hour at 37° C. For optimal sensitivity, the factor VII value of the normal plasma is adjusted to approximately 20% because the factor VII assay is more sensitive in this area of the curve. In addition, an excess of patient's plasma will make the test more sensitive to small amounts of inhibitors.(Owen CA Jr, Bowie EJW, Thompson JH Jr: The Diagnosis of Bleeding Disorders. Second edition. Little, Brown, and Company, 1975, pp 143-145; Meijer P, Verbruggen and Spannagi M: Chapter 33: Clotting factors and inhibitors: Assays and Interpretation. In Laboratory Hematology Practice. Edited by K Kottke-Marchant. Wiley Blackwell Publishing, 2012, pp 435-446)
If the inhibitor screen is positive for an inhibitor of factor VII, the inhibitor will be quantitated by the "Bethesda assay." In the Bethesda procedure, inhibitors are quantified by mixing equal volumes of serially diluted plasma with normal plasma. This mixture is incubated 2 hours at 37° C, and its factor VII activity is measured and compared to a control run at the same time. The difference between the factor VII activity of the patient's incubation mixture and that of the control is used to calculate titer. The residual factor VII activity is converted to "Bethesda units": 50% residual factor VII is equal to 1 Bethesda unit.(Kasper CK, Aldedort LM, Counts RB, et al: A more uniform measurement of factor VIII inhibitors. Thromb Diath Haemorrh 1975;34:869-872; Meijer P, Verbruggen and Spannagi M: Chapter 33: Clotting factors and inhibitors: Assays and Interpretation. In Laboratory Hematology Practice. Edited by K Kottke-Marchant. Wiley Blackwell Publishing, 2012, pp 435-446)
Day(s) Performed
Monday through Friday
Report Available
1 to 3 daysTest Classification
This test has been modified from the manufacturer's instructions. Its performance characteristics were determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
85390-FVII Tech Interp
85230-Factor VII
85335-Factor inhibitor (if appropriate)
85335-Bethesda units (if appropriate)
85390-Factor VII Professional interp (if appropriate)
LOINC Code Information
| Test ID | Test Order Name | Order LOINC Value |
|---|---|---|
| 7INHE | Factor VII Inhib Profile, P | 90225-4 |
| Result ID | Test Result Name | Result LOINC Value |
|---|---|---|
| F_7 | Coag Factor VII Assay, P | 3198-9 |
| 7INHT | FVII Inhib Profile Tech Interp | 69049-5 |
Forms
If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.