The CUSUM Slope Equals Observed Minus Expected Mortality and Can Be Visualized by a "Slope-Meter"

Ann Thorac Surg. 2022 Sep;114(3):640-642. doi: 10.1016/j.athoracsur.2022.05.022. Epub 2022 May 30.

Abstract

We present an additional advantage of the Risk-Adjusted CUSUM (RA-CUSUM), namely, that its slope can be quantified and is in fact equivalent to Observed (O) minus Expected (E) mortality. That is, the height of the RA-CUSUM is the O minus E deaths, which measures performance since the start of the series, and the slope of the RA-CUSUM is the O minus E mortality which measures performance during a chosen interval. We present a useful graphical tool (Slope-Meter) to allow approximation of this mortality difference by the viewer.