Advantages of CUSUM techniques for quality control in clinical chemistry.

The performance of routine analytical laboratories is assessed, inter alia, by the use of appropriate internal quality control techniques. Despite evidence that the cumulative sum technique is generally superior to Shewhart-type control charts and many others, its use has been limited by the popular misconception that it is inferior to Shewhart's in detecting large variations and/or outliers in quality control data. The application of computer simulation methods has enabled us to answer this criticism and has provided the basis for further improvements in the design of the appropriate control scheme for general use in clinical chemistry.