Center differences in diabetes treatment outcomes among children with type 1 diabetes: A nationwide study of 3866 Danish children

Objective: Mean differences in HbA_1c across centers are well established, but less well understood. The aim was to assess whether differences in patient case-mix can explain the variation in mean HbA_1c between pediatric diabetes centers in Denmark. The association between HbA_1c, frequency of blood glucose monitoring (BGM), treatment modality, and center visits was investigated. Research Design and Methods: This longitudinal nationwide study included 3866 Danish children with type 1 diabetes from 2013 to 2017 (n = 12,708 child-year observations) from 16 different pediatric diabetes centers. Mean HbA_1c, proportion of children reaching HbA_1c treatment target (HbA_1c ≤ 58 mmol/mol [7.5%]) were compared across centers using linear regression models. This was done with and without adjustment for socioeconomic characteristics (patient case-mix). Results: The mean difference in HbA_1c during follow-up was 11.6 mmol/mol (95% CI 7.9, 15.3) (1.1% [95% CI 0.7, 1.4]) when comparing the centers with the lowest versus highest mean HbA_1c. The difference was attenuated and remained significant after adjustment for the patient case-mix (difference: 10.5 mmol/mol [95% CI 6.8, 14.2] (1.0% [95% CI 0.6, 1.3])). Overall, 6.8% of the differences in mean HbA_1c across centers were explained by differences in the patient case-mix. Across centers, more frequent BGM was associated with lower HbA_1c. The proportion of insulin pump users and number of visits was not associated with HbA_1c. Conclusion: In a setting of universal health care, large differences in HbA_1c across centers were found, and could not be explained by patient background, number of visits or use of technology. Only BGM was associated with center HbA_1c.