Test ID: F8INH
Factor VIII Inhibitor Evaluation
Secondary ID 
A test code used for billing and in test definitions created prior to November 2011
NY State Approved Indicates the status of NY State approval and if the test is orderable for NY State clients.
Useful For Suggests clinical disorders or settings where the test may be helpful
Detecting the presence and titer of a specific factor inhibitor directed against coagulation factor VIII
Profile Information A profile is a group of laboratory tests that are ordered and performed together under a single Mayo Test ID. Profile information lists the test performed, inclusive of the test fee, when a profile is ordered and includes reporting names and individual availability.
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| F8A | Coag Factor VIII Activity Assay, P | Yes | Yes |
Reflex Tests Lists test(s) that may or may not be performed, at an additional charge, depending on the result and interpretation of the initial test(s)
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| IBETH | Bethesda Units | No | No |
| F8IS | Coag Factor VIII Assay Inhib Scrn,P | No | No |
| CCCR | Special Coagulation Interpretation | No | No |
Testing Algorithm Delineates situation(s) when tests are added to the initial order. This includes reflex and additional tests.
Testing begins with coagulation factor VIII activity assay with dilutions to evaluate assay inhibition; if the factor VIII activity assay is decreased, an inhibitor screen will be performed to look for specific factor VIII inhibition. If specific inhibition is apparent, the titer of the inhibitor will be determined.
Special Instructions and Forms Describes specimen collection and preparation information, test algorithms, and other information pertinent to test. Also includes pertinent information and consent forms to be used when requesting a particular test
Method Name A short description of the method used to perform the test
F8A/9070: Activated Partial Thromboplastin Clot-Based Assay
F8IS/7289, IBETH/7288: Clot-Based Assay
Reporting Name A shorter/abbreviated version of the Published Name for a test; an abbreviated test name
Aliases Lists additional common names for a test, as an aid in searching
Specimen Type Describes the specimen type needed for testing
Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.
See Coagulation Studies in Special Instructions.
Specimen Type: Platelet-poor plasma
Collection Container/Tube: Light-blue top (citrate)
Submission Container/Tube: Plastic vials
Specimen Volume: 3 mL in 3 plastic vials each containing 1 mL
Collection Instructions:
1. Specimen must be drawn prior to factor replacement therapy.
2. Spin down, remove plasma, and spin plasma again.
3. Freeze specimens immediately at < or =-40 degrees C, if possible.
4. Send specimens in the same shipping container.
Additional Information:
1. Double-centrifuged specimen is critical for accurate results as platelet contamination may cause spurious results.
2. If priority specimen, mark request form, give reason, and request a call-back.
3. Each coagulation assay requested should have its own vial.
Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.
Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected
| Hemolysis | Mild OK; Gross reject |
| Lipemia | Mild OK; Gross reject |
| Icterus | Mild OK; Gross reject |
| Other | NA |
Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.
| Specimen Type | Temperature | Time |
|---|---|---|
| Plasma Na Cit | Frozen | 14 days |
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Factor VIII inhibitors are IgG antibodies directed against coagulation FVIII that typically result in development of potentially life-threatening hemorrhage. These antibodies may develop in 1 of 4 different patient populations:
-Patients with congenital FVIII deficiency (hemophilia A) in response to therapeutic infusions of factor VIII concentrate
-Elderly nonhemophiliac patients (not previously factor VIII deficient)
-Women in postpartum period
-Patients with other autoimmune illnesses
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
FACTOR VIII ACTIVITY ASSAY
Adults: 55-200%
Normal, full-term newborn infants or healthy premature infants usually have normal or elevated factor VIII.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
FACTOR VIII INHIBITOR SCREEN
Negative
BETHESDA TITER
0 Units
Interpretation Provides information to assist in interpretation of the test results
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 Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
This test is not useful for detecting the presence of inhibitors directed against other clotting factors and will not detect the presence of lupus anticoagulants.
If presence or type of inhibitor is unknown, PROCT/83097 Prolonged Clot Time Profile or LUPPR/83092 Lupus Anticoagulant Profile should be ordered.
Occasionally, a potent lupus-like anticoagulant may cause false-positive results for a specific factor inhibitor (eg, factor VIII or IX). See preceding caution statement.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
1. Kasper CK: Treatment of factor VIII inhibitors. Prog Hemost Thromb 1989;9:57-86
2. Peerschke EI, Castellone DD, Ledford-Kraemer M, et al: Laboratory assessment of FVIII inhibitor titer. Am J Clin Pathol 2009;131(4):552-558
3. Pruthi RK, Nichols WL: Autoimmune factor VIII inhibitors. Curr Opin Hematol 1999;6(5):314-322
Method Description Describes how the test is performed and provides a method-specific reference
The factor VIII assay is performed on the Beckman Coulter ACL TOP using the activated partial thromboplastin time (APTT) method and a factor deficient substrate. Patient plasma is combined and incubated with a factor VIII deficient substrate (normal plasma depleted of factor VIII by immunoadsorption) and an APTT reagent. After a specified incubation time, calcium is added to trigger the coagulation process in the mixture. At which time, the time to clot formation is measured optically using a wavelength of 671 nm. (Owen CA Jr, Bowie EJW, Thompson JH Jr: Diagnosis of Bleeding Disorders. 2nd edition. Boston, MA, Little, Brown and Company, 1975)
The factor VIII inhibitor screen consists of measuring the difference in factor VIII activity (partial thromboplastin time 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 VIII value of the normal plasma is adjusted to approximately 20%, because the factor VIII 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. 2nd edition. Boston, MA, Little, Brown, and Company, 1975, pp 143-145)
If the inhibitor screen is positive for an inhibitor of factor VIII, 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 VIII activity is measured and compared to a control run at the same time. The difference between the factor VIII activity of the patient's incubation mixture and that of the control is used to calculate the titer. The residual factor VIII activity is converted to Bethesda units: 50% residual factor VIII is equal to 1 Bethesda unit. Assays using the same basic principle as the Bethesda assay are used to quantitate the inhibitors of the other coagulation factors. (Kasper CK, Aldedort LM, Counts RB, et al: A more uniform measurement of factor VIII inhibitors. Thromb Diath Haemorrh 1975;34:869-872)
Day(s) and Time(s) Test Performed Outlines the days and times the test is performed. This field reflects the day and time the sample must be in the testing laboratory to begin the testing process and includes any specimen preparation and processing time required before the test is performed. Some tests are listed as continuously performed, which means assays are performed several times during the day.
Monday through Friday; Varies
Analytic Time Defines the amount of time it takes the laboratory to setup and perform the test. This is defined in number of days. The shortest interval of time expressed is "same day/1 day," which means the results may be available the same day that the sample is received in the testing laboratory. One day means results are available 1 day after the sample is received in the laboratory.
Maximum Laboratory Time Defines the maximum time from specimen receipt at Mayo Medical Laboratories until the release of the test result
Specimen Retention Time Outlines the length of time after testing that a specimen is kept in the laboratory before it is discarded
Performing Laboratory Location The location of the laboratory that performs the test
Test Classification Provides information regarding the medical device classification for laboratory test kits and reagents. Tests may be classified as cleared or approved by the US Food and Drug Administration (FDA) and used per manufacturer's instructions, or as products that do not undergo full FDA review and approval, and are then labeled as an Analyte Specific Reagent (ASR), Investigation Use Only (IUO) product, or a Research Use Only (RUO) product.
CPT Code Information Provides guidance in determining the appropriate Current Procedural Terminology (CPT) code(s) information for each test or profile. The listed CPT codes reflect Mayo Medical Laboratories interpretation of CPT coding requirements. It is the responsibility of each laboratory to determine correct CPT codes to use for billing.
85240-Factor VIII activity assay
85335-Bethesda titer (if appropriate)
85335-Factor VIII inhibitor screen (if appropriate)
85390-26-Special coagulation interpretation (if appropriate)
LOINC® Code Information Provides guidance in determining the Logical Observation Identifiers Names and Codes (LOINC) values for the result codes returned for this test or profile.
| Result ID | Reporting Name | LOINC Code |
|---|---|---|
| F8A | Coag Factor VIII Activity Assay, P | 3209-4 |
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