Anticardiolipin antibodies (IgA)

Anticardiolipin antibodies (ACA) are detected and quantified using indirect enzyme-linked immunosorbent assay (ELISA). The ACA produced as part of the autoimmune response in antiphospholipid syndrome are in fact directed to a cryptic epitope in Domain I of β2glycoprotein I (β2GPI) that is exposed during a conformational change induced in β2GPI when it binds to negatively charged phospholipid. ACA in patient sera are captured in microtitre plates coated with cardiolipin and β2GPI. Unbound material is then washed and a solution of antibody to human immunoglobulin that is conjugated to an enzyme is added to ‘tag’ onto any captured ACA. 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 ACA capture and thus, ACA 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. IgA anticardiolipin antibody assays are recommended as second-line diagnostic tests."
Reference range: 


APL U/ml
Sample type and Volume required: 
External requests: serum
350µL x 1 aliquot
Internal requests: please refer to EPR label

Turnaround time: 
Contact laboratory
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.

Print as a PDF

Last updated: 08/03/2017