DiaPharma Group, Inc.

For in vitro diagnostic use.

An enzyme-linked immunosorbent assay (ELISA) for the semi-quantitative determination of IgM anti-Beta 2 Glycoprotein l (b2GPl) antibodies in human serum. For the detection and semi-quantitation of IgM anti-b2GPl antibodies in individuals with systemic lupus erythematosus (SLE) and lupus-like disorders (anti-phospholipid syndrome).

• For the specific determination of IgM anti-B2GP1 antibodies
• Excellent clinical correlation
• Color coded reagents
• Total incubation time: 40 minutes
• Convenient, cost effective
• Choice of single or multi-point calibration

Background

Anti-phospholipid antibodies are a heterogeneous group of antibodies that bind to several anionic phospholipids. Most autoimmune anti-phospholipid antibodies require serum cofactors for optimal binding.

Beta 2 Glycoprotein I (B2GPI) is a protein cofactor with natural anticoagulant properties and has an affinity for negatively-charged phospholipids. Antibodies directed against B2GPI have been shown to be associated with thrombosis in individuals with systemic lupus erythematosus (SLE) and lupus-like disorders (antiphospholipid syndrome).

The presence of both anti-phospholipid and anti-B2GP1 antibodies shows a better correlation with the clinical manifestations of antiphospholipid syndrome than either of these antibodies occurring separately.

Principle

REAADS AB2GPI ELISA

The REAADS IgM anti-B2GPI Test Kits are indirect enzyme linked immunosorbent assays for the semiquantitative determination of anti-B2GP1 antibodies in human serum. A single point or multi point calibrator is used to measure IgM anti-B2GP1 antibody concentrations in M units.

Procedure

Diluted patient serum is incubated in wells coated with purified human B2GP1. Anti-B2GP1 antibodies, if present, will bind to the antigen coated wells. Following a wash to remove any unbound serum or plasma, antibodies specific to human IgG labeled with horseradish peroxidase (HRP) are added to the wells. After washing to remove unbound conjugate, a chromogenic substrate is added, resulting in a soluble colored product that is measured in a spectrophotometer at 450nm following the addition of a stop solution.

Relative patient anti-B2GP1 levels are determined by comparing the absorbance of patient wells to those of the calibrator. The results of the REAADS anti-B2GP1 test are expressed in M units. Total incubation is 40 minutes at room temperature.

Clinical Performance

Clinical Specificity: serum samples from multiple healthy blood donor populations were assayed for the presence of IgG, IgM, IgA anti-B2GPI antibodies. Specificity was shown to be 100%, 93%, and 96%, respectively for the three isotypes.

Clinical Sensitivity: an unselected SLE population was tested to determine the clinical sensitivity of the anti-B2GPI assays.

Sensitivity was 23% for IgG, 20% for IgM and 25% for IgA. The clinical sensitivity of the assay for thrombosis was determined by comparing anti-B2GPI test results from two groups of selected SLE patients: Group 1, with a clinical history of thrombosis and/or thrombocytopenia; and Group 2, with no history of thrombosis (control). The results are shown below: