Westgard J O, Groth T, Aronsson T, de Verdier C H
Clin Chem. 1977 Oct;23(10):1881-7.
We describe the adaptation of the decision limit cumulative sum method (cusum) to internal quality control in clinical chemistry. With the decision limit method, the cusum is interpreted against a numerical limit, rather than by use of a V-mask. The method can be readily implemented in computerized quality-control systems or manually on controls charts. We emphasize the manual application here and demonstrate how the technique can be implemented on existing Shewhart or Levey-Jennings control charts. This permits both cusum and Shewhart control rules to be used simultaneously on a single control chart and also minimizes the data calculations necessary for the cusum method. Computer simulation studies are used to determine the performance characteristics of several different cusum rules, alone and in combination with a Shewhart rule. These studies indicate that improvements in existing quality-control systems should be possible by addition of this simple cusum method and by use of a combined Shewhart-cusum control chart. This should be particularly advantageous when introducing the cusum method in laboratories with manual quality-control systems.
我们描述了决策限累积和法（cusum）在临床化学室内质量控制中的应用。采用决策限法时，累积和是对照一个数值界限进行解释的，而不是使用V形模板。该方法可在计算机化质量控制系统中轻松实现，也可在控制图上手动操作。我们在此强调手动应用，并演示如何在现有的休哈特或利维-詹宁斯控制图上实施该技术。这使得累积和控制规则与休哈特控制规则能在同一张控制图上同时使用，同时也将累积和法所需的数据计算减到最少。通过计算机模拟研究来确定几种不同累积和规则单独使用以及与休哈特规则联合使用时的性能特征。这些研究表明，通过添加这种简单的累积和法以及使用休哈特-累积和联合控制图，有可能改进现有的质量控制系统。在采用手工质量控制系统的实验室引入累积和法时，这应该特别有利。
