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.
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 |
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 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.
Optical Clot-Based
Factor VII Inhibitor Screen, Plasma
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.
Plasma Na Cit
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.
Send all vials in the same shipping container.
If priority specimen, mark request form, give reason, and request a call-back.
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 degrees C or, ideally, < or =-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.
If not ordering electronically, complete, print, and send a Coagulation Test Request (T753) with the specimen.
2 mL in 2 plastic vials, 1 mL each
Gross hemolysis | Reject |
Gross lipemia | Reject |
Gross icterus | Reject |
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Plasma Na Cit | Frozen | 14 days |
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.
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.
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.
FACTOR VII ACTIVITY ASSAY
Adults: 65-180%
Normal, full-term newborn infants or healthy premature infants may have decreased levels (> or =20%), which increase within the first postnatal week but may not reach adult levels for > or =180 days postnatal.*
*See Pediatric Hemostasis References in Coagulation Guidelines for Specimen Handling and Processing in Special Instructions.
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.
Occasionally, a potent lupus-like anticoagulant may cause false-positive testing for a specific factor inhibitor (eg, factor VIII or IX); see Ordering Guidance.
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
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 degrees 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 degrees 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)
Monday through Friday
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.
85390-FVII Tech Interp
85230-Factor VII
85335-Factor inhibitor (if appropriate)
85335-Bethesda units (if appropriate)
85390-Factor VII Professional interp (if appropriate)
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
7INHE | Factor VII Inhib Profile, P | 90225-4 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
F_7 | Coag Factor VII Assay, P | 3198-9 |
7INHT | FVII Inhib Profile Tech Interp | 69049-5 |