Exploring Variation in Glycemic Control Across and Within Eight High-Income Countries: A Cross-sectional Analysis of 64,666 Children and Adolescents With Type 1 Diabetes.

Abstract

International studies on childhood type 1 diabetes (T1D) have focused on whole-country mean HbA_1c levels, thereby concealing potential variations within countries. We aimed to explore the variations in HbA_1c across and within eight high-income countries to best inform international benchmarking and policy recommendations. Data were collected between 2013 and 2014 from 64,666 children with T1D who were <18 years of age across 528 centers in Germany, Austria, England, Wales, U.S., Sweden, Denmark, and Norway. We used fixed- and random-effects models adjusted for age, sex, diabetes duration, and minority status to describe differences between center means and to calculate the proportion of total variation in HbA_1c levels that is attributable to between-center differences (intraclass correlation [ICC]). We also explored the association between within-center variation and children's glycemic control. Sweden had the lowest mean HbA_1c (59 mmol/mol [7.6%]) and together with Norway and Denmark showed the lowest between-center variations (ICC ≤4%). Germany and Austria had the next lowest mean HbA_1c (61-62 mmol/mol [7.7-7.8%]) but showed the largest center variations (ICC ∼15%). Centers in England, Wales, and the U.S. showed low-to-moderate variation around high mean values. In pooled analysis, differences between counties remained significant after adjustment for children characteristics and center effects (<i>P</i> value <0.001). Across all countries, children attending centers with more variable glycemic results had higher HbA_1c levels (5.6 mmol/mol [0.5%] per 5 mmol/mol [0.5%] increase in center SD of HbA_1c values of all children attending a specific center). At similar average levels of HbA_1c, countries display different levels of center variation. The distribution of glycemic achievement within countries should be considered in developing informed policies that drive quality improvement.