STANDARDIZATION OF ELISA FOR THE DETECTION OF ANTICARDIOLIPIN ANTIBODIES - EFFECT OF NONSPECIFIC IGG BINDING

Various frequencies of anti-cardiolipin antibodies reported in patients with systemic lupus erythematosus and other autoimmune and infectious diseases necessitates the need for standardization of the immunoassay. We report here the usefulness of "no-antigen" control for each serum in determining the actual value of the anti-phospholipid antibodies. This non-specific "no-antigen" binding was quite variable from serum to serum and in general was higher in the patient population than in healthy individuals which served as controls. This non-specific binding may be associated with the increased IgG content of the sera as shown by the linear association of the absorbance of the back-ground readings to increases in IgG concentration (correlation coefficient 0.98).