Inter-rater variability for the American Society of Anesthesiologists classification in patients undergoing hepato-pancreato-biliary surgery (MILESTONE-2): international survey among surgeons and anaesthesiologists.

Background: Patients undergoing hepato-pancreato-biliary surgery are typically preoperatively assessed using the American Society of Anesthesiologists (ASA) classification, which is also used for case-mix adjustment when comparing centre outcomes. Studies determining the inter-rater variability of the ASA classification within hepato-pancreato-biliary surgery are currently lacking.

Methods: An international survey was collected and a case-vignette study was performed (November 2022-April 2023) regarding the ASA classification in patients undergoing hepato-pancreato-biliary surgery among anaesthesiologists and surgeons from (inter)national societies. The survey consisted of 23 questions and eight case-vignettes. Primary analysis included descriptive statistics and the inter-rater variability was calculated using Light's Kappa.

Results: Overall, 1283 participants from 55 countries responded: 1073 (84%) anaesthesiologists and 210 (16%) surgeons. The ASA classification was commonly used, both clinically 1003/1283 (78%) and for research 728/762 (96%). The majority of respondents (n = 1019, 79%) declared that ASA score impacted their perioperative strategy. There inter-rater variability was fair-moderate (Kappa 0.26-0.42) in all case-vignettes. Inter-rater variability differed within and among geographic regions for each case. Over 80% (n = 1138) of respondents stated that they would take the underlying disease (for example cancer) into account, but this changed the preferred ASA score within the case-vignettes by only 1%. Type of surgery changed the preferred score in the case-vignettes (13% difference). The most common suggestions to improve the ASA classification were to clarify whether type of operation should be considered, create a more extensive definition, and provide more examples.

Conclusions: Inter-rater variability was present within the ASA classification of patients undergoing hepato-pancreato-biliary surgery, which may impact perioperative strategy and hamper research results. Additional guidance to classify patients according to ASA is urgently needed. Until then, more objective measurements should be considered for case-mix adjustment within research.