Description:

The Diagnostic Automation Beta(ß)-2GP1 IgA Enzyme-linked Immunosorbent Assay (ELISA) is intended for the detection and semi quantitative determination of IgA antibodies to β2GP1 in human sera or plasma. The results of the assay are to be used as an aid in the diagnosis of certain autoimmune disease thrombotic disorders, anti-phospholipid syndrome, SLE or lupus-like disorders.

Cardiolipin auto antibodies (ACA) are described for various autoimmune diseases. The presence of anticardiolipin antibodies in systemic lupus erythematosus (SLE) can be related to the development of thrombocytopenia, in gynecology they are supposed to cause intrauterine death or recurrent abortion. Furthermore, anti-cardiolipin antibodies have been found in some non-thrombotic neurological disorders like cerebrovascular insufficiency, cerebral ischemia or chorea and in myocardial infarction. Recent studies have shown that a 50kD serum cofactor is required for anticardiolipin antibodies, to bind to cardiolipin which has been coated onto plastic plates. The cofactor has been identified as β2-glycoprotein 1 also termed apolipoprotein H. β2GP1 has been known as an in vitro inhibitor of the intrinsic blood coagulation pathway, ADP-dependent aggregation, and prothrombinase activity of activated platelets. It has become apparent that anticardiolipin antibody from patients with anti-phospholipid syndrome (APS) recognize a modified β2GP1 structure and not cardiolipin, native β2GP1 or an epitope structurally defined by both cardiolipin and β2GP1. Galli and Viard reported that anti-cardiolipin antibody derived from SLE and APS were directed to the β2GP1 molecule coated on polystyrene plates. Koike and Matsuura showed conclusively that β2GP1 is indeed the antigen to which many anticardiolipin antibody patients are actually binding and furthermore showed that the phospholipid merely serves to link the β2GP1 to the solid phase. β2GP1 auto antibodies are found in the immunoglobulin classes IgG, IgM and IgA. The determination of IgM antibodies is a valuable indicator in the diagnosis of beginning autoimmune disease, whereas IgG and/or IgA antibodies will be found in progressive stages of manifested autoimmune disorders. IgA antibodies are often associated with IgG antibodies. The determination of IgA antibodies seems to have a greater validity in thrombosis and fetal loss. Indications for determination of anti β2GP1 antibodies are: SLE, Thrombosis, Thrombocytopenia, Cerebral Ischemia, Chorea, Epilepsy, Recurrent Abortion and Intrauterine Death.

Purified β2GP1 antigens are coated on the surface of microwells. Diluted patient serum or plasma, and calibrators, are added to the wells. The Anti β2GP1 specific antibodies, if present, bind to the antigens. All unbound materials are washed away. After adding enzyme conjugate, it binds to the antibody-antigen complex. Excess enzyme conjugate is washed off, and TMB Chromogenic substrate is added. The enzyme conjugate catalytic reaction is stopped at a specific time. The intensity of the color generated is proportional to the amount of IgA specific antibodies in the sample. The results are read by a microwell reader, and compared in a parallel manner with calibrators.