Factor VIII inhibitor (ELISA)

Description: 
FVIII antibodies can be detected using indirect enzyme-linked immunosorbent assay (ELISA). FVIII antibodies in patient sera, whether inhibitory or 'immune', are captured in microtitre plates coated with recombinant FVIII. Unbound material is then washed off and a solution of antibody to human immunoglobulin that is conjugated to an enzyme is added to ‘tag’ onto any captured FVIII antibodies. Unbound conjugate is washed off and a substrate for the enzyme is added, the product of the enzyme-substrate reaction being coloured. Colour intensity is in direct proportion to the degree of conjugate-binding, itself proportional to the amount of FVIII antibody capture. The assay is not quantitative and is reported as either positive or negative based on whether the colour intensity exceeds a kit-specific cut-off value.
Clinical details: 
Acquired inhibitors to FVIII are antibodies that arise in 10-15% of patients with hereditary haemophilia A as a result of recognising therapeutic FVIII products as 'foreign' protein, or in patients with previously normal haemostasis as part of an autoimmune process. Inhibitors in congenital haemophiliacs complicate treatment as the infused FVIII has a shorter survival time, and patients with acquired haemophilia can present with severe bleeding. Some patients generate antibodies that are not inhibitory but may cause increased clearance upon removal of immune complexes from the circulation.
Related condition or disease: 
Haemophilia A, acquired haemophilia
Reference range: 

Not detected

Department: 
Haemostasis and Thrombosis Department
Location: 
St Thomas' Hospital
Sample type and Volume required: 
External requests: Citrated platelet poor plasma
150µL x 1 aliquot
Internal requests: please refer to EPR label

Turnaround time: 
7 - 10 days
Special sample instructions: 

The sample should be analysed or manipulated & stored in the laboratory within 4 hours of venepuncture.

Criteria for acceptance / rejections of sample
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
For clinical advice or interpretation of results, please contact the laboratory in the first instance.
Laboratory: 
Diagnostic Haemostasis and Thrombosis Laboratory at Guy's and St Thomas'

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Last updated: 09/03/2017