Internal Quality Control in Medical Laboratories: Westgard and the Others

This review recalls some ISO 15189:2022 requirements for the management of examination results and emerging alternatives for internal quality control (IQC), in relation to Italian Society of Clinical Pathology and Laboratory Medicine (SIPMeL) Recommendations Q19. We have observed phenomena of contrasting “metrological,” or rather “tracealogic,” and “statistical” approaches. SIPMeL Recommendation Q19 picks up IQC with moving average from ISO 15189, which provides for the use of moving average of patient sample results (MA). In the veterinary field the procedure of QC with repeat testing on patient samples (RPT-QC) has met with some success. The “bayesian approach” of IQC making use of the distinction between a priori probability, evidential probability (data) and a posteriori probability (IQC rules). SIPMeL recommendations Q19 strictly adhere to ISO 15189:2022 document. SIPMeL Q19 calls for abandoning the 1-2s rule, using appropriate computer tools, not only control charts, and trying to reduce false positives to very low frequencies. The alternatives to IQC with patient results and Bayesian approach are compatible with ISO 15189 and SIPMeL Q19. In contrast, the alternative with material designed for traceability, with assigned value, is not compatible with ISO standard.