Research article

CUSUM: A tool for early feedback about performance?

Winston R Chang^*† and Ian P McLean^†

• * Corresponding author: Winston R Chang wins71@yahoo.com

• † Equal contributors

Author Affiliations

From the Department of Trauma & Orthopaedics, Dumfries and Galloway Royal Infirmary, Bankend Road, Dumfries, DG1 4AP, UK

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BMC Medical Research Methodology 2006, 6:8 doi:10.1186/1471-2288-6-8

Published: 2 March 2006

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.