Chapter 5 - Issues of Interferences in Clinical Chemistry Tests Including Heterophilic Antibody Interferences

Abstract

Various factors such as age, gender, diet, and exercise may affect analyte values but assay interferences, although infrequent, must be taken seriously because wrong laboratory test results may cause wrong diagnosis and unnecessary therapy, as approximately 70% of all diagnoses are based on laboratory test results. When laboratory test result does not correlate with clinical presentation of a patient, assay interference should be considered. Endogenous factors such as high bilirubin, hemolysis, and lipemia, as well as presence of autoantibodies, rheumatoid factors, and heterophilic antibodies, may cause assay interference. Similarly, exogenous factors such as a drug or drug metabolite can also cross-react with the assay antibody causing erroneous results. Reanalyzing a specimen using a different assay platform is a straightforward approach to overcome assay interference. Nonlinearity upon dilution is also a strong indication of assay interference. Various approaches including pretreatment of specimen with polyethylene glycol, heterophilic antibody–blocking agent, size exclusion gel chromatography, etc. are useful in overcoming interferences due to the presence of heterophilic antibodies in the specimen.