Factor IX inhibitor (Bethesda)
- Description
- Dilutions of test plasma (i.e. reducing concentrations of inhibitor) are incubated for a short period (30 minutes) at 37oC in the presence of a fixed amount of exogenous FIX in the Bethesda assay. One unit of inhibitor is defined as the amount of inhibitor that will neutralise 50% of a normal plasma containing 100% FIX. The amount of residual FIX in each tube is used to calculate the inhibitor level.
- Clinical details
- Acquired inhibitors to FIX are antibodies that arise in 1.5 - 3% of patients with hereditary haemophilia B as a result of recognising therapeutic FIX products as 'foreign' protein, or very rarely, in patients with previously normal haemostasis as part of an autoimmune process. Inhibitors in congenital haemophiliacs complicate treatment as the infused FIX has a shorter survival time, and patients with acquired haemophilia can present with severe bleeding.
- Related condition
- Reference range
Not detected
- Units
- BU/ml
- Testing site
- Synnovis : Blood Sciences : St Thomas' Hospital
- Laboratory
- Diagnostic Haemostasis and Thrombosis
- Sample type and volume required
- External requests: Citrated platelet poor plasma 1mL x 1 aliquot Internal requests: please refer to EPR label
- Special sample instructions
The sample should be analysed or manipulated & stored in the laboratory within 4 hours of venepuncture. Please ensure sample tubes are filled exactly to the fill-line as underfilling creates a dilution error and leads to inaccurate results.
- Turnaround time
- 7 - 10 days
- Contacts
Diagnostic Haemostasis and Thrombosis Department
St Thomas’ Hospital
Phone: 020 7188 2797
St Thomas’ Hospital
North Wing – 4th and 5th Floors
Westminster Bridge Road
London SE1 7EHGuy’s Hospital
Phone: 020 7188 7188 ext. 53860
Guy’s Hospital
Southwark Wing – 4th Floor
Great Maze Pond
London SE1 9RT
Outside core hours, contact Duty Haemostasis Biomedical Scientist