Developing an evidence-based approach to quality control.

• The underlying assumptions of conventional quality control (QC) are described. • The limitations of the application of the Sigma metric in calculating QC frequency are described. • An alternative, patient-based real-time quality control, is presented with its advantages and disadvantages. Effective Quality Control remains one of the pillars of Clinical Biochemistry. An understanding of the possible analytical errors that may occur, how to detect them efficiently and how to prevent them from causing patient harm are critical components of a Quality System. For some time, there have been questions about the theoretical basis of the models used to describe and detect analytical error. The current theory recognises two types of error, systematic and random and a system based on sampling the analytical process using a synthetic material to detect these errors. However, there are at least two other errors that are present. One is related to the QC material and the other, irregular errors. In this Opinion Piece, some of the underlying assumptions of Quality Control systems are described and analysed. [ABSTRACT FROM AUTHOR]