We have read the article of Drs Mueller and Matthews on the “impact of robotic operative efficiency on profitability” with interest and have several questions.

First, it appears that very little information is provided about the assumptions that were made for the calculation of costs. Specifically, how did the authors approach the allocation of “indirect” and “fixed” costs? This report is essentially the publication of a decision analysis and yet any other decision analysis that we have seen published in this journal includes an exhaustive description of the underlying assumptions used in the decision analytic model. Measuring the actual organizational resource use associated with surgical and inpatient care is notoriously complex. When comparing the cost of different interventions, this is of less importance because the assumptions are shared across different interventions. However, when trying to judge the absolute “profitability” of a specific service the assumptions used for the allocation of indirect costs become much more important to the ultimate conclusion.

Our second question stems from the analysis of the data that was presented, which seems to show the per-case cost of robotic surgeries going up with time and increased volume. The only reason the program appears to be more “profitable” as time goes on is that reimbursements increased more than costs. Because there is no information on case-mix/acuity, it leaves the reader with the impression that the only reason that the program is doing better financially is because they are capturing more revenue per case. Yet the authors seem to imply that improved efficiency and higher volume are the pathways to “profitability” for robotic programs.

Finally, in the discussion the authors state “a similar reduction in operative cost was demonstrated for gynecologic procedures at Brigham and Women’s Hospital (Boston, MA), where robotic procedural case time decreased significantly over the study period.” This is not correct. In that study (authored by one of us [J.E.]), we found no significant decrease in procedural time for robotic cases, whereas we found a significant reduction in operating room time in the laparoscopic, nonrobotic, group. We also found that the robotic hysterectomies were associated with the highest operating room cost in both 2006 and in 2009. In addition, we would like to point out that we retracted the findings for total hospital cost and societal cost in a separate letter to the editor.

One final point: it appears that references 18 and 19 are not citing the correct paper and this needs to be corrected.

We look forward to the views of the authors and/or editors on these matters.