Author Response to Commentary on “A cumulative sum (CUSUM) analysis studying operative times and complications for a surgeon transitioning from laparoscopic to robot-assisted pediatric pyeloplasty: Defining proficiency and competency

The authors wish to thank the reviewer for their comments which are apt and relevant regarding the use of CUSUM analysis for operative learning curves. Specifically, that the CUSUM curve for operative time is likely to show a similar pattern for other surgeons, if they choose to construct the learning curve using their own means, because mathematically, subtracting the mean from each datapoint will eventually reach zero at the last datapoint. It is therefore true that if constructed on an objectively accepted mean other than one's own that the learning curve for individual surgeons may not necessarily reach the “competency” phase according to the well-accepted standard. The value however lies in identifying the cut points to monitor the learning progression of a single surgeon and would be even more beneficial if data from several centers or surgeons is combined in a CUSUM analysis. It is then going to be a valuable tool for assessing training progression when a well-accepted standard is not available as a reference. One additional important factor, which made the learning progression appear rapid in this study is the fact that a pyeloplasty is a very standardized procedure and although anatomical variations exist, they are much more infrequent than, for example, a hypospadias repair. The authors also acknowledge that operative time alone is a poor marker for competency, the value of the CUSUM analysis in setting alert and alarm levels for complications, is probably equally if not more valuable in assuring safe progression of the learning curve. However, in a universal funded healthcare system like Canada, there is value in showing a predictable decrease in operative times. The additional costs of new technology can be offset by decrease in operative times significantly, as each hour of operative room time, in our system, for example, conservatively is around 1200 Canadian dollars. This allows the surgeon initiating a new technique, in a universal healthcare model, to present a more efficient and palatable model to healthcare administrators. This is even more pertinent because despite some observational studies suggesting that robot-assisted approach is associated with a shorter length of stay than open pyeloplasty and a shorter learning curve than laparoscopic pyeloplasty, there is currently no Level 1 evidence to demonstrate a clear cost benefit advantage of a robot assisted approach for pediatric pyeloplasty versus a laparoscopic/open approach [ , ].