Risk-Adjusted Monitoring Method for Surgical Data: Methodology for Data Analytics (Work in Progress)
BACKGROUND Conventional assessment of the outcome of cardiac surgery usually takes the form of retrospective mortality figures and, at best, indicates an average performance over time. Summary tables conceal good and bad runs, and without risk adjustment they are difficult to interpret. We developed a refinement of the cumulative sum method that weights death and survival by each patient's risk status and provides a display of surgical performance over time. METHODS The variable life-adjusted (VLAD) plot shows the difference between expected and actual cumulative mortality. VLAD shows whether a surgeon's performance is above or below what might be expected. This mortality-scoring system accumulates penalties for each death and rewards for every survivor, based on the inherent risk of perioperative death of each case concerned. FINDINGS We illustrate the results of three performance reviews, displayed as VLADs. The first shows the results of an individual surgeon for 547 consecutive cardiac-surgical cases. The overall mortality was 36% less than that predicted by the Parsonnet scoring system. The second displays the results for 5000 consecutive patients who underwent cardiopulmonary bypass between 1992 and 1996, divided into six contemporaneous series. The predicted mortality was 9% compared with 6% actual mortality. The third is a plot for a trainee surgeon and clearly shows how a period of poor performance was identified and then substantially improved, which would not have been revealed by conventional tables of summary statistics. INTERPRETATION VLAD provides a graphical display of risk-adjusted survival figures for individual surgeons or units over time and could be modified to monitor performance over a range of treatments and outcomes.