Monitoring surgical quality: the cumulative sum (CUSUM) approach

Abstract

Monitoring the quality of new or ongoing surgical activities is a necessity. Several Statistical Process Control (SPC) tools are available to professionals. Among them, Shewhart charts and cumulative sum charts (CUSUM charts) are useful methods to provide visual feedback before significant quality issues arise. In this paper, we discuss both methods based on our current approach. On Shewhart charts, one variable value is plotted on a time-series line. This method provides information about every single determination. Random variations of the values appear and by adjusting the adequate control limits it is possible to know whether those variations are random or out-of-control. Although large variations are easily detected, small but relevant changes are not. On the contrary, CUSUM charts have the capability of detecting small changes quickly. CUSUM is defined as a statistical tool that graphically represents the sequential monitoring of cumulative performance of any dichotomized or continuous variable under assessment. It emphasizes failures penalizing them against the correct performance when individual risk is adjusted. This makes CUSUM especially sensitive to negative changes. CUSUM can be created without the need of a specific sample size and grow with every new case included. Besides the variable under control (with specific definitions of acceptable and unacceptable outcomes), the type I and II errors for the defined parameter and the individual risk of acceptable or unacceptable outcomes must be included in the chart. Graphical representation of these three parameters is easy and intuitive to read making CUSUM graphs a reliable tool to understand the trending of the parameter under control. If performance is considered inadequate: analysis, discussion and implementation of agreed measures should be taken. Despite its limitations, CUSUM analysis is considered the best tool for quality control in health care domain.

Evaluation of physician experience in achieving non-perfused volume ratio of high-intensity focused ultrasound ablation for uterine fibroids: a multicentre study

“… 22 , 23 A previous study reported that an HIFU ablation of uterine fibroids that achieved an immediate NPVR of at least 80% was safe. 14 Recently, researchers have set the NPVR at a minimum of 80% as a measure of sufficient ablation in the HIFU ablation therapy of uterine fibroids. 25 , 26 Even some researchers have shown that an NPVR of 90% can be used as a standard for the HIFU ablation therapy of uterine fibroids.…”

“…11,12 The cumulative recurrence rate in 2 years was less than 10% when 70% of NPVR was achieved, which was similar to that of myomectomy. 13,14 Recently, with the increasing clinical application of HIFU technology, the effectiveness of NPVR ! 80% and NPVR !…”

“…90% have also been reported. [14][15][16] Experienced physicians achieved better results than inexperienced physicians when NPVR ! 80% was the criteria for technical success.…”

“… 11 , 12 The cumulative recurrence rate in 2 years was less than 10% when 70% of NPVR was achieved, which was similar to that of myomectomy. 13 , 14 Recently, with the increasing clinical application of HIFU technology, the effectiveness of NPVR ≥ 80% and NPVR ≥ 90% have also been reported. 14 – 16 Experienced physicians achieved better results than inexperienced physicians when NPVR ≥ 80% was the criteria for technical success.…”

“… 13 , 14 Recently, with the increasing clinical application of HIFU technology, the effectiveness of NPVR ≥ 80% and NPVR ≥ 90% have also been reported. 14 – 16 Experienced physicians achieved better results than inexperienced physicians when NPVR ≥ 80% was the criteria for technical success. 10 However, there has not been any studies reported on the learning curve of physicians under the three standards of NPVR ≥ 70%, NPVR ≥ 80% and NPVR ≥ 90%.…”