Validation of Obesity Surgery Data in the Swedish National Patient Registry and Scandinavian Obesity Registry (SOReg)

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.