Interferences in hormone immunoassays

Analytic interferences occur infrequently with immunoassays, but false positive or false negative results can have major clinical consequences. This article contrasts the differences between competitive and immunometric (sandwich) immunoassays and illustrates how various potential interferences, including heterophile antibodies, autoantibodies, rheumatoid factor, and cross-reacting substances, may cause problems with specific assay formats. Mechanisms to detect the interferences and correct the problems are outlined. The clinical significance of these interferences is illustrated by reviewing selected published cases.