Variation in outcomes after metabolic bariatric surgery: multilevel analysis to assess the contribution of patient, surgeon, and hospital factors.

BACKGROUND Metabolic bariatric surgery (MBS) quality registries monitor various outcomes, enabling the assessment of hospital performance in comparison with national benchmarks. However, if there is considerable between-surgeon outcome variation, surgeon-level feedback may be better suited. The aim of this study was to assess the extent to which patient-, surgeon-, and hospital-level factors contribute to the variation in outcomes after MBS. METHODS All primary procedures registered in the Dutch MBS quality registry between 1 January 2020 and 31 December 2023 were included. Outcomes included severe postoperative complications, reoperation, prolonged length of stay (LOS), readmission, textbook outcome, and achieving ≥25% total weight loss within 1 year. Multilevel logistic regression models were built for each outcome, including all available patient characteristics, operating surgeon, and hospital, to determine the variance explained by patient-, surgeon-, and hospital-level factors. RESULTS In total, 30 610 patients were included, operated on by 144 surgeons in 19 hospitals. Hospital-level factors contributed most to the explained variance for all outcomes, ranging from 59.6% for reoperation to 90.3% for prolonged LOS. Surgeon-level factors explained less variance, ranging from 3.2% for prolonged LOS to 28.2% for reoperation. Patient characteristics explained the least, ranging from 4.4% for textbook outcome to 13.1% for severe postoperative complications. CONCLUSION Variation in outcomes is mostly explained by hospital factors, rather than surgeon factors, supporting hospital-based performance feedback. The results suggest that the pre- and postoperative trajectory and perioperative care may affect MBS outcomes more than patient characteristics or surgical team performance.