Statistical quality control: overview of applications in the clinical laboratory

The role of quality control in the laboratory has changed substantially over the last 70 years (Fig 1). Quality requirements have changed in line with developments in technology, automation and efficiency, leading to quality improvement being firmly established in working practices. It is the role of quality control (QC) within this context that will be covered in this series.

Using internal quality control (IQC) as a surrogate for assay performance is familiar to us in pathology laboratories. We often use it as the basis of our quantification of measurement uncertainty. Statistical quality control (SQC) is the next generation of IQC. For it to be useful we need to be assured that we are using the right quality control process… and doing it right.

It is unsurprising that we in pathology laboratories did not come up with the idea of quality control. In industry, statistical measures, and their application to quality processes, are commonplace. Ranging from the Student’s t-test – developed as a measure of quality control in Guinness production in 1908 by William Gosset¹ – to the advent of Six Sigma processes in the 1980s, quality control has been used throughout industry to drive quality improvement.