Plasma interference in an enzyme-linked immunosorbant assay using a commercial matched antibody pair

In this study, severe plasma interference was repeatedly documented in an I L-1ra sandwich enzyme-linked immunosorbant assay (ELISA) using a commercial matched antibody pair. Several physical and biochemical treatments were us ed in an attempt to alleviate this plasma effect including the following: b uffer optimization, sample dilution, increasing incubation temperature, hea t treatment of plasma, increasing detergent concentrations, glutaraldehyde pretreatment of the plate and the addition of polyethylene glycol (PEG). Ev aluation of several buffers demonstrated that the range of optical densitie s could be increased dramatically with the use of an appropriate buffer. Of the treatments examined, only the addition of polyethylene glycol (PEG) to the dilution buffer created a marked improvement in the ELISA, despite a r esulting background increase. Further investigation demonstrated that 10% P EG in the dilution buffer added to biotinylated antibody and the streptavid in provided the greatest improvement to the sensitivity of the ELISA.