Risk-Adjusted Cumulative Sum Control Charting Procedures.

Abstract

<P>RISK-ADJUSTED CHARTS FOR MONITORING THE PERFORMANCES OF A SURGEON OR A GROUP OF SURGEONS HAVE RECENTLY GAINED THEIR PROMINENCE IN THE LITERATURE. IT STARTED WITH THE INTRODUCTION OF A CHART THAT PLOTS CUMULATIVELY THE EXPECTED MORTALITY COUNTS MINUS THE OBSERVED COUNTS IN 1997. THE STATISTIC PLOTTED IS INTUITIVE AND IT HAS GAINED WIDESPREAD ATTENTION AND ADOPTION. HOWEVER, THE RUN LENGTH PERFORMANCE OF THIS CHART IS STILL NOT CLEARLY UNDERSTOOD BECAUSE OF THE LACK OF A SIGNALLING RULE. A CUMULATIVE SUM CHART BASED ON TESTING THE ODDS RATIO THAT A PATIENT DIES WAS PROPOSED IN 2000. THE RUN LENGTH PERFORMANCE OF THIS CHART IS OPTIMAL BUT THE INTERPRETATION OF THIS CHART IS NOT AS EASY BECAUSE OF THE INHERENT DIFFICULTY IN INTERPRETING ODDS RATIO. BETWEEN 2000 AND 2008, MANY PAPERS WERE PUBLISHED COMPARING THESE TWO CHARTS. ALTHOUGH THESE TWO CHARTS LOOK SEEMINGLY DIFFERENT, WE SHOW THAT THEY ARE IN FACT MATHEMATICALLY IDENTICAL AND WE PRESENT A UNIFIED APPROACH BASED ON TESTING THE RI