Background: The Swiss-Finnish Bariatric Metabolic Outcome Score (SF-BARI Score), based on merged data of two RCTs, is a composite endpoint designed to evaluate and categorize outcomes after metabolic bariatric surgery (MBS). The aim of this study was to externally validate the score using registry data.

Methods: Individual patient data were included from the Dutch Audit for Treatment of Obesity, the Scandinavian Obesity Surgery Registries (SOReg-Sweden and SOReg-Norway), and the merged RCT data used for establishing the SF-BARI Score. All patients undergoing primary MBS from January 2010 to June 2018, with complete baseline characteristics, as well as complete 1- and 5-year follow-up data, were included. The mean total score and distribution were compared between the combined registry and merged RCT data.

Results: There was no statistically significant difference in the mean SF-BARI Score between the registries (21 603 patients) and merged RCTs (457 patients) at 5 years (90.9 versus 89.1 points; difference = 1.8 (95% c.i. -1.0 to 4.7); P = 0.212), and the score distribution was similar. Statistically significant differences in baseline characteristics existed regarding sex (male 20.9% versus 29.3%), type 2 diabetes (16.7% versus 33.9%), hypertension (30.4% versus 66.1%), dyslipidaemia (13.7% versus 46.5%), obstructive sleep apnoea syndrome (12.0% versus 17.4%), and sleeve gastrectomy (SG) rate (21.0% versus 49.9%) (P < 0.001). The mean score estimate at 5 years in Roux-en-Y gastric bypass was 11.2 (95% c.i. 10.2 to 12.2) points higher compared with SG (P < 0.001).

Conclusion: This study verified the feasibility of the SF-BARI Score, enabling standardized reporting and allowing for comparison of different treatment modalities.