Performance specifications and six sigma theory: Clinical chemistry and industry compared

Analytical performance specifications are crucial in test development and quality control. Although consensus has been reached on the use of biological variation to derive these specifications, no consensus has been reached which model should be preferred. The Six Sigma concept is widely applied in industry for quality specifications of products and can well be compared with Six Sigma models in clinical chemistry. However, the models for measurement specifications differ considerably between both fields: where the sigma metric is used in clinical chemistry, in industry the Number of Distinct Categories is used instead. In this study the models in both fields are compared and discussed. •The Six Sigma model is a leading quality system in both industry and clinical chemistry.•The sigma metric is used in industry to express the quality of production and transactional processes.•There are significant differences in the application of the sigma metric between industry and clinical chemistry.•The Number of Distinct Categories (NDC) is a flawless Six Sigma metric to express the quality of a measuring procedure.