The impact of quality control materials on the performance of an internal quality control system: 1. General...

Quality assurance in clinical chemistry is based on statistical control procedures designed to maintain a certain level of quality. Decisions about acceptance or rejection of analytical series are made primarily from measurements of quality control materials. Such materials are most often of non-human origin; this may lead to false decisions due to non-identity of patient samples and quality control material. We have investigated the significance of non-identity between patient and control materials by running two separate quality control systems in parallel. A regular system used for acceptance or rejection of series, and a parallel system used for registration of the actual quality of the analytical routine work. The results from the latter system have not been available for the operator handling the control system used in routine work. Our study has confirmed the validity of an internal quality control system to achieve a certain level of analytical stability as expressed by the short-term and long-term precision. However, because ideal control materials are not always available, additional procedures to control accuracy, specificity, and detectability may be necessary. The usefulness of such procedures to properly handle error signals from quality control systems has been demonstrated.