Endogenous and exogenous interferences in thyroid function immunoassays

Abstract

Laboratory diagnosis of endocrine diseases has undergone many important changes over the past decades, despite the progress of thyroid function immunoassays technologies interferences cannot be completely excluded. These interferences can affect measurement of analyte which leads to misinterpretation and subsequent wrong clinical decisions, the probability of which is about 1%. However, the scale of the problem may be greater due to the lack of awareness to the problem among doctors and the lack of laboratory screening for interfering factors. These factors can be both endogenous and exogenous, bind both to antibodies to the analyte and to the reagent in the test system. The specificity of the immunoassay depends not only on the binding properties of antibodies, the activity of reagent, but also on the composition of the test system and the format of the methodology (non-competitive two-site or “sandwich” and competitive assays). This review provides a description of the main interferences that can affect the measurement of thyroid hormones, in particular thyroid stimulating hormone, free thyroxine and triiodothyronine, calcitonin, and demonstrates clinical cases reported in the literature over the past few years.