Antiprothrombin antibodies (IgG & IgM)

Antiprothrombin antibodies are detected and quantified using indirect enzyme-linked immunosorbent assay (ELISA). Antiprothrombin antibodies in patient sera are captured in microtitre plates coated with purified prothrombin. 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 antiprothombin 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 antibody capture and thus, antiprothombin antibody concentration.
Clinical details: 
The antiphospholipid syndrome (APS) is a systemic autoimmune disorder characterised clinically by vascular thrombosis and/or pregnancy morbidity. APS is diagnosed in patients who present with these clinical signs and symptoms and demonstrate the persistent presence of antiphospholipid antibodies.

Criteria antibodies for diagnosis of APS are lupus anticoagulant, anticardiolipin antibodies and/or β2 glycoprotein I antibodies. Persistence of one or more of these antibodies in the presence of appropriate clinical manifestations secures diagnosis of APS, although association and recurrence are higher in patients with multiple-positivity. Antiprothombin antibodies are not considered 'criteria' antibodies although opinion/experience is divided and they may be useful in some patients. The assay can also be used in patients who present with bleeding symptoms due to concomitant 'immune' antibodies that are not inhibitory but lead to removal of prothrombin from the circulation.
Reference range: 

Positive anti-prothrombin IgG antibodies:>  8.0 G U/mL        

Positive anti-prothrombin IgM antibodies:> 4.0 M U/mL

G U/ml (IgG) M U/ml (IgM)
Sample type and Volume required: 
Serum (SST)
Turnaround time: 
7 - 12 days
Special sample instructions: 

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

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

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.

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Last updated: 24/01/2022