Endogenous interference in imunoassays in clinical chemistry. A rewiev

Abstract

Weber TH, Kapyaho KI & Tanner P Endogeneous interference in immunoassays in clinical chemistry. A review. Scand . I Clin Lab Invest 1990; 50, Suppl201: 77-82.The increasing availability and use of immunoassays in clinical chemistry have revealed a number of endogeneous interferences. Solid-phase sandwich immunoassays based on monoclonal antibodies are particularly sensitive to any factor able to bridge immunoglobulins together. Heterophilic immunoglobulin antibodies have been demonstrated in up to 40 % of patient samples and to cause spuriously elevated results unless certain precautions are taken. Rheumatoid factors belong to the same category, but their affinity is usually too low to cause significant interference. Immunoscintigraphy generates high-titre anti-immunoglobulin responses causing serious interferences in immunoassays. Recently interfering factors of unknown nature causing nonspecific binding of enzyme-labelled antibodies have been observed. Spuriously decreased values can be caused by complement, which may interfere with antigen-binding to solid phase antibody. The aforementioned and other endogeneous interferences in immunoassays are reviewed and methods for their elimination discussed.

Heterophilic antibodies may be a cause of falsely low total IGF1 levels

“…Therefore, it is routine practice for assay manufacturers to incorporate the serum of nonimmune animal species in the reagents of most methods. Bovine serum has been shown to be more efficient than murine serum (29). It has been suggested that heterophilic antibodies in most patients are bovine IgGs arising from the ingestion of meat and milk (13).…”

7 Immunoassay interference – How to recognize, eliminate, or reduce it

“…The occurrence of heterophilic antibodies in samples of human serum or plasma in the population was estimated at 30%-40% (29,30). Their concentration in the blood and detectability by using different methods depend on the type of antibody.…”

“…Various immunoassay buffer additives may reduce interference from heterophilic antibodies. Although mouse IgG is most frequently used in the currently accessible noncompetitive immunoassays, bovine serum has been shown to be more efficient than murine serum in blocking heterophilic antibodies (72). Practically no information on this matter can be found in the literature.…”

Interference in immunoassay is an underestimated problem

“…Fragments, rather than the intact antibody, have been used in an attempt to reduce interference from antibodies against the Fc region, which are produced in some conditions such as autoimmune disease. 8,11,42 However, because interfering antibodies mainly interact with binding sites on the Fab region, the use of a fragment rather than the entire antibody as a reagent may reduce, but not eliminate, insidious interference.…”