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HelpTest ID F9INH Factor IX Inhibitor Evaluation
Useful For
Detection and titering of coagulation inhibitor to the specific factor requested, primarily factor IX in patients with hemophilia B
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| F_9 | Coag Factor IX Assay, P | Yes | Yes |
Reflex Tests
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| IBETH | Bethesda Units | No | No |
| F9_IS | Factor IX Inhib Scrn | No | No |
| CCCR | Special Coagulation Interpretation | No | No |
Testing Algorithm
Testing begins with coagulation factor IX activity assay with dilutions to evaluate assay inhibition; if the factor IX activity assay is decreased, an inhibitor will be performed to look for specific factor IX inhibition. If specific inhibition is apparent, it will be titered.
Special Instructions
Method Name
F_9: Activated Partial Thromboplastin Time-Based Clotting Assay
F9_IS, IBETH: Clot-Based Assay
Reporting Name
Factor IX Inhib ProfileSpecimen Type
Plasma Na CitSee 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 ≤-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.
Forms: If not ordering electronically, complete, print, and send a Coagulation Test Request Form (T753) with the specimen (http://www.mayomedicallaboratories.com/it-mmfiles/coagulation-test-request-form.pdf)
Specimen Minimum Volume
2 mL
Specimen Stability Information
| Specimen Type | Temperature | Time |
|---|---|---|
| Plasma Na Cit | Frozen | 14 days |
Clinical Information
Factor IX inhibitors arise in patients with severe hemophilia B after factor IX transfusion. Patients with factor IX inhibitors may also develop anaphylactic reactions in response to factor IX infusions. Acquired factor IX inhibitors, occurring in previously healthy people, are exceedingly rare.
Reference Values
FACTOR IX ACTIVITY ASSAY
Adults: 65-140%
Normal, full-term newborn infants or healthy premature infants may have decreased levels (≥20%), which may not reach adult levels for ≥180 days postnatal.*
*See Pediatric Hemostasis References in Coagulation Studies in Special Instructions.
FACTOR IX INHIBITOR SCREEN
Negative
BETHESDA TITER
0 Units
Cautions
This test is not useful for detecting presence of inhibitors directed against other clotting factors and is not useful for the detection of a nonspecific circulating anticoagulant.
This assay will not detect presence of lupus anticoagulants.
If presence or type of inhibitor is unknown, PROCT / Prolonged Clotting Time or LUPPR / Lupus Anticoagulant Profile should be ordered.
Occasionally, a potent lupus-like anticoagulant may cause false-positive testing for a specific factor inhibitor (eg, factor VIII or IX). See preceding caution statement.
Day(s) Performed
Monday through Friday; Varies
Report Available
1 dayPerforming Laboratory
Mayo Medical Laboratories in Rochester
CPT Code Information
85250-Factor IX activity assay
85335-Bethesda titer (if appropriate)
85335-Factor IX inhibitor screen (if appropriate)
85390-26-Special coagulation interpretation (if appropriate)