Cumulative sum techniques for surgeons: a brief review

There has been increasing awareness of the need for monitoring the quality of health care, particularly in the area of surgery. The Cumulative Summation (Cusum) techniques have emerged as a popular tool for performance monitoring in surgery. They allow one to judge whether a given variation in performance is probably due to chance or greater than could be expected from random variation and thus a cause for concern. The Cusum techniques are simple to carry out and can be applied to any surgical process with a binary outcome. Four parameters need to be set in advance: acceptable outcome rate, unacceptable outcome rate, Type I and Type II error rates. In this article, we review the history, statistical methods and potential applications for the Cusum techniques in the field of surgery and illustrate the two common forms of charting (cumulative failure and Cusum charting) by using unadjusted outcome data from the Geelong Hospital and St Vincent's Hospital cardiac surgery databases.