Comparison of risk adjusted excess post‐operative pancreatic fistula rates after pancreaticoduodenectomy using cumulative sum analysis

Abstract

Background: Post-operative pancreatic fistula (POPF) is a key outcome post pancreaticoduodenectomy. There are numerous POPF risk calculators but no agreed benchmark, a key component of meaningful audit. We compared observed versus predicted POPF for six risk adjusted POPF calculators, to ascertain how they differ and thus contribute to discussion around benchmarking. Methods: This was a retrospective single-arm cohort study at the Royal Melbourne Hospital of patients who underwent pancreaticoduodenectomy 1 November 2015 to 31 December 2021 with a primary outcome of a clinically relevant POPF. Cumulative sum (CUSUM) plots of observed versus predicted rate of POPF for sequential patients were constructed for six risk adjusted POPF calculators -Birmingham, updated Birmingham, fistula risk score (FRS), modified FRS (m-FRS), alternative FRS (a-FRS), and updated alternative FRS (ua-FRS).Results: The study included 77 patients. The actual rate of clinically relevant POPF was 14.3%. FRS calculated an excess of 1.3 POPF per 100 cases. All other calculators demonstrated prevention of POPF per 100 cases: Birmingham 3.4, updated Birmingham 14.0, m-FRS 0.3, a-FRS 1.2, ua-FRS 19.7. Conclusion:The observed versus predicted rate of POPF was near zero for all risk calculators except ua-FRS and updated Birmingham, which predicted a higher POPF than observed (19.7, 14.0, respectively). These results indicate that, excepting ua-FRS and updated Birmingham, these calculators yield comparable results. Benchmarks for POPF should prescribe which risk calculators are used, and ideally a unified standard between centres should be the goal to provide consistency in outcome reporting and robust audit processes.