Cholangiography during laparoscopic cholecystectomy - Cumulative sum analysis of an institutional learning curve

The ability to perform intraoperative cholangiography during laparoscopic c holecystectomy is an essential skill for the laparoscopic biliary surgeon. The volume of experience required to be able to consistently obtain a chola ngiogram during laparoscopic cholecystectomy has not been determined. Cumul ative sum analysis is a statistical technique which generates a graphical d isplay that identifies periods of performance that fall below a predetermin ed standard for a given task. The cumulative sum (S-n for a series of obser vations is defined as: S-n = (i=1)Sigma(n)X(i) - X-o, where X-i = 0 for a s uccess, X-i = 1 for a failure, and X-o is the acceptable failure rate for t he process under study. This function is plotted against the number of obse rvations to create a curve. When the curve has a positive slope, the accept able failure rate is being exceeded. When it reaches a plateau, the observe d failure rate is equal to the acceptable failure rate. When the curve has a negative slope, the observed failure rate is lower than the acceptable fa ilure rate. We performed a cumulative sum analysis of the first 97 intraope rative cholangiograms attempted during laparoscopic cholecystectomy at our institution. The results demonstrated that 46 cases were required to reach a level of proficiency where a cholangiogram could be obtained in 95% of at tempts. Success rates of 85% and 90% were achieved at 16 and 25 cases, resp ectively. This form of analysis is a useful tool for estimating the number of attempts required to achieve a desired success rate when learning new pr ocedures.