Interferences in Immunoassays

Interference in immunoassays is a serious but underestimated problem (Ismail et al, 2002a). Interference is defined as “the effect of a substance present in the sample that alters the correct value of the result, usually expressed as concentration or activity, for an analyte” (Kroll & Elin, 1994). Immunoassays are analytically sensitive and measurements can frequently performed without prior extraction. However, immunoassays may lack adequate specificity and accuracy. Specificity of an immunoassay does not only depend on the binding property of the antibody but also the composition of the antigen and its matrix is important. Specificity can also be influenced by reagent composition and immunoassay format. Substances that alter the measurable concentration of the analyte in the sample or alter antibody binding can potentially result in assay interference (Tate & Ward, 2004).