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Factor IX Assay
Test CodeFACIX
Alias/See Also
Factor 9, Antihemophilic Factor B, Factor, IX
CPT Codes
85250
Preferred Specimen
Citrate BLUE (BLU)
Instructions
Collect whole blood in 3.2% buffered sodium citrate (9:1 blood to sodium citrate). Venipuncture must be atraumatic.
Specimen Stability
- Centrifuge at 4,500 RPM (high) for 10 minutes. Plasma platelet count should be less than 10,000. Test within four hours of collection.
- If testing is to be delayed more than four hours after collection, immediately separate plasma into a clean, polystyrene tube, cap and store below -20°C up to two weeks or -70°C up to six months.
- In patients with hematocrit values greater than 55%, the citrate concentration must be adjusted so that a proper plasma/anticoagulant volume is maintained.
Reject Criteria (Eg, hemolysis? Lipemia? Thaw/Other?)
Reject hemolyzed, clotted, overfilled tubes or short draw (<90%) samples
Reference Range
Normal Range:
- 1 day -6 years of age: 15-91%
- > 6 years of age: 50-150%
Clinical Significance
Use to diagnose factor IX deficiency (hemophilia B) and monitor factor IX replacement therapy.
Performing Laboratory
CRMC Laboratory
