Laboratory results are a key enabler of disease diagnosis and the management of effective treatment. Therefore, clinical laboratories have a responsibility, often mandated, to provide results that are fit for those purposes. This means the assays must have stable characteristics and produce consistent results from day to day. Quality systems such as ISO 15189 have been produced by the international laboratory medicine community to provide a management and technical structure to assist laboratories in achieving these goals [1]. The Quality system includes governance processes, document control, equipment maintenance, staff training, and competence requirements to provide the essential supporting framework to build the capability needed to create and produce consistent results. However, the essential process that must be understood and utilised every day by most technical staff to produce patient results is the principles of quality control (QC).