Medical biology laboratories rely especially on internal quality control (IQC) to monitor the performance of equipment and ensure results reliability. Strategies for these controls vary considerably from one laboratory to another. Some laboratories use Westgard's rules to detect drifts and are faced with a large number of false rejections caused by frequent runs of control samples and strategies that activate all rejection rules, regardless of the analyte considered. To minimize these rejections, some laboratories have combined several theories, sometimes despite the relevance of the resulting strategy. In this article, we want to explain the foundations of the main IQC theories and set out a strategy to optimize the detection of problems while minimizing false IQC rejections. We will also address some frequently asked questions from laboratories as part of ISO 15189 accreditation.
Keywords: internal quality control; laboratory medicine; rules.