CUSUM: a tool for early feedback about performance?

Abstract

Background: Modern day clinical practice demands evidence justifying our choice of treatment methods. Cumulative sum techniques (cusum) are amongst the simplest statistical methods known. They provide rapid analysis and identification of trends in a series of data. This study highlights use of these techniques as an early performance indicator of a clinical procedure before its implementation.

Methods: Twenty consecutive patients who underwent total hip or knee arthroplasty received a simple dressing--blue gauze and Tegaderm. Cusum charting was used to assess the dressing with regards to skin blistering. At an acceptable level of performance the curve would oscillate about the horizontal axis and the overall trend therefore said to be flat. If performance is unacceptable, the cusum slopes upward.

Results: The cusum plot for the twenty patients did not cross the specified control limits. This showed that our simple dressing met specified standards with regards to wound blistering postoperatively.

Conclusion: We recommend the use of this simple, yet versatile cusum technique in the early evaluation of a clinical procedure before its implementation.

Figure 1

A V-Mask demonstrating an out of control process.

Figure 2

Cusum plot for joint replacement wound blisters using blue gauze and Tegaderm as the wound dressing.