Interference in immunoassays is insidious and could adversely affect patient care

The success of analytical methods in clinical chemistry has led to a sense of security in the value of laboratory results. This is largely justified, as evidenced by the quality of laboratory performance assessed by external assurance schemes. Nevertheless, it is not widely recognised among clinicians that some biochemical tests are more prone to interference from unusual serum constituents than others—and that quality assurance schemes can do little about this.

An important example of this is tests carried out by immunoassays based on the recognition of molecules by antibodies. The antibodies are largely derived from animal sources and are typically used for measuring hormones, tumour markers, cardiac troponins, and therapeutic drugs and for viral serology.

The design of assays has evolved enormously since the discovery of immunoassay by Berson et al in 1956,1 and it is now a major analytical tool in clinical laboratories worldwide, allowing relatively minute (picomole (10⁻¹²)) amounts of analytes to be measured with unrivalled precision.

Interference …