Factor VIII Inhibitor (Emicizumab insensitive Nijmegen Bethesda assay utilising chromogenic Bovine based reagents)
Description:
Inhibitors to coagulation Factor VIII (FVIII) are antibodies that may occur in 10-15% of patients with congenital Haemophilia A. The Nijmegen Bethesda assay is based on the measurement of FVIII recovery values following incubation of test plasma with reference standand. One unit of inhibitor is defined as the amount that will neutralise 50% of a reference plasma containing 100% FVIII after a 2 hour incubation. Emicizumab (Hemlibra) is a bispecific antibody which acts as a coagulation FVIII mimetic unaffected by FVIII inhibitors. Emicizumab is insensitive to FVIII chromogenic assay where bovine based reagents are used. This assay modification allows FVIII inhibitors to be measured during emicizumab therapy.
This test is not currently included in the laboratory's UKAS scope of accreditation to ISO15189:2012.
This test is not currently included in the laboratory's UKAS scope of accreditation to ISO15189:2012.
Clinical details:
Emicizumab has a longer half life in the circulation than convential FVIII replacement therapy and may be prescribed where FVIII inhibitors are detected. Monitoring of FVIII inhibitory activity requires the use of an emicizumab insensitive assay. The bovine based FVIII Nijmegen Bethesda allows for the measurement of anti-FVIIII antibodies during emicizumab therapy.
Reference range:
Not detected
Synonyms or keywords:
Hemlibra, EHL, emicizumab, bovine
Units:
NBU/mL
Department:
Location:
Sample type and Volume required:
External requests: Citrated platelet poor plasma (1mL x 1 aliquot) or 3.5mL whole blood citrate Internal requests: please refer to EPR label
Turnaround time:
7-12 days
Special sample instructions:
The sample should be analysed or processed & stored within 4 hours of venepuncture. Please ensure sample tubes are filled exactly to the fill-line as underfilling or overfilling creates a dilution error and leads to inaccurate results.
Storage and transport:
It is advised that citrated plasma is frozen prior to transport and sent to the laboratory on dry ice to maintain sample quality and integrity. Whole blood can be sent at room temperature, but must be received within 4 hours of venepuncture. Suggest laboratory contacted in advance of sample dispatch.
Contacts:
Diagnostic Haemostasis and Thrombosis Department
St Thomas': 020 7188 2797; Guy's: 020 7188 7188 ext. 53860
St Thomas' Hospital
North Wing - 4th and 5th Floors
Westminster Bridge Road
London SE1 7EH
Laboratory opening times
24/7
Guy's Hospital
Southwark Wing - 4th Floor
Great Maze Pond
London SE1 9RT
Outside core hours, contact Duty Haemostasis Biomedical Scientist
North Wing - 4th and 5th Floors
Westminster Bridge Road
London SE1 7EH
Laboratory opening times
24/7
Guy's Hospital
Southwark Wing - 4th Floor
Great Maze Pond
London SE1 9RT
Outside core hours, contact Duty Haemostasis Biomedical Scientist
Last updated: 05/11/2021
