The potency of immunoglobulin G fragments for inhibition of interference caused by anti-immunoglobulin antibodies in a monoclonal immunoradiometric assay for thyrotropin
Csako, G.; Weintraub, B.D.; Zweig, M.H.
Clinical Chemistry 34(7): 1481-1483
1988
ISSN/ISBN: 0009-9147 PMID: 3260545 Document Number: 307499
Heterophile antibodies in patients' serum may produce false increases in apparent analyte concentrations in "sandwich"-type immunoassays. Using three patients with endogenous anti-mouse IgG antibodies and a two-site mouse monoclonal assay for thyrotropin we studied the ability of IgG fragments to block this positive interference. Mouse whole IgG and IgG Fc fragments blocked the interference virtually completely; IgG F(ab')2 and Fab fragments did not. Rat and horse immunoglobulin fragments gave variable results. We suggest that sandwich assays formulated with IgG Fab or F(ab')2 fragments may be less susceptible to positive interference by heterophile antibodies. Unlike sera from the three patients, simulated human specimens containing heterologous anti-IgG antibodies showed little or no selectivity in inhibition by IgG fragments, and therefore are not useful to study this phenomenon.