Use of Control Charts to Monitor Post-Cataract Surgery Acute Endophthalmitis in Spain

Abstract

Purpose: : To employ statistical process control methods to determine if the rate of post-operative endophthalmitis following cataract surgery at a single institution is in statistical control.

Methods: : Data on all patients who underwent cataract surgery between January 2004 and December 2008 at the Hospital de León was prospectively collected. Utilizing statistical process control charts, we analyzed the rate of endophthalmitis in these patients in order to detect trends in variation of the rate of endophthalmitis over time. SPC XL 2007 software was used to construct: (1) g-charts of the days between endophthalmitis cases in the hospital; (2) run charts of the rate of cases of endophthalmitis over time.

Results: : A total of 5,013 cataract surgeries were performed. The run chart illustrated a mean annual incidence of endophthalmitis of 0.18%, although in 2005 a markedly higher incidence of 0.61% was documented. Use of the g-chart revealed that over this 5-year time period, the mean number of days between endophthalmitis cases was 141 and the longest number of days between cases was 365. Use of these charts helped detect significant variation in outcomes in 2005, which led the hospital to introduce intraocular Cefuroxime as a component of surgical care. Since the intervention of Cefuroxime in June 2006, only two new cases of endophthalmitis occurred.

Conclusions: : This study represents the first use of statistical process control charts to analyze endophthalmitis rates in Spain. Control chart analysis provided data on temporal variation in outcomes, allowing the identification of a need to augment current practice. Furthermore, control charts also provided a means by which to determine the success of the measures introduced. Traditional engineering tools, such as control charts, provide a powerful method of monitoring eye care services data to identify changes in processes of care and points of improvement in the quality of the delivery of eye services.

Keywords: cataract • endophthalmitis