title: Validation of Obesity Surgery Data in the Swedish National Patient Registry and Scandinavian Obesity Registry (SOReg).
abstract: Swedish health registries are common sources of data for studies on the effects of obesity surgery, and there is a need to assess the quality of data in these registries. The aim of this study was to validate the registration of obesity surgery in the National Patient Registry (NPR) and the Scandinavian Obesity Surgery Registry (SOReg).
  
  
  
  We randomly selected 962 out of 8501 registrations of obesity surgery in 2011 from the NPR and SOReg. Registered surgical procedures in the NPR and SOReg were compared to the medical records, and concordance was analyzed by calculating positive predictive value (PPV) with 95 % confidence interval (CI).
  
  
  
  We received 938 (98 %) medical records for manual review. The overall PPV for obesity surgery was high in the NPR (PPV 97.0; 95 % CI 95.6-98.4) and even higher in SOReg (PPV 99.7; 95 % CI 99.3-100). Accuracy was higher for gastric bypass surgery than for other types of obesity surgery. Registrations that were misclassified as obesity surgery (n = 44) included reoperations due to complications or reconstruction to normal anatomy after previous obesity surgery (n = 11) and endoscopic procedures (n = 10).
  
  
  
  Obesity surgery registrations in the NPR and SOReg have high accuracy and are reliable sources of data to identify patients having undergone obesity surgery. When it is of importance to distinguish between specific surgical procedures, non-gastric bypass surgeries in the NPR should ideally be supplemented with data from other sources.
authors.affiliation: Upper Gastrointestinal Surgery, Department of Molecular medicine and Surgery, Karolinska Institutet, Norra Stationsgatan 67, 171 76, Stockholm, Sweden. wenjing.tao@ki.se.
authors.forename: Wenjing
authors.initials: W
authors.lastname: Tao
authors.affiliation: Upper Gastrointestinal Surgery, Department of Molecular medicine and Surgery, Karolinska Institutet, Norra Stationsgatan 67, 171 76, Stockholm, Sweden.
authors.forename: Dag
authors.initials: D
authors.lastname: Holmberg
authors.affiliation: Department of Clinical Sciences, Danderyd Hospital, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Erik
authors.initials: E
authors.lastname: Näslund
authors.affiliation: Department of Surgery, Faculty of Medicine and Health, Örebro University, Örebro, Sweden.
authors.forename: Ingmar
authors.initials: I
authors.lastname: Näslund
authors.affiliation: Upper Gastrointestinal Surgery, Department of Molecular medicine and Surgery, Karolinska Institutet, Norra Stationsgatan 67, 171 76, Stockholm, Sweden.
authors.forename: Fredrik
authors.initials: F
authors.lastname: Mattsson
authors.affiliation: Upper Gastrointestinal Surgery, Department of Molecular medicine and Surgery, Karolinska Institutet, Norra Stationsgatan 67, 171 76, Stockholm, Sweden.|Section of Gastrointestinal Cancer, Division of Cancer Studies, King's College London, London, UK.
authors.forename: Jesper
authors.initials: J
authors.lastname: Lagergren
authors.affiliation: Unit of Epidemiology, Institute of Environmental Medicine, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Rickard
authors.initials: R
authors.lastname: Ljung
mesh_terms: D050110:Bariatric Surgery / Q000706:statistics & numerical data*; D019985:Benchmarking; D006801:Humans; D009767:Obesity, Morbid / Q000453:epidemiology* / Q000601:surgery; D012042:Registries / Q000592:standards* / Q000706:statistics & numerical data; D015203:Reproducibility of Results; D013548:Sweden / Q000453:epidemiology
keywords: Bariatric surgery; Cohort; Metabolic surgery; Obesity; Quality