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

Dimitrios Charalampopoulos, Julia M Hermann, Jannet Svensson, Torild Skrivarhaug, David M Maahs, Karin Akesson, Justin T Warner, Reinhard W Holl, Niels H Birkebæk, Ann K Drivvoll, Kellee M Miller, Ann-Marie Svensson, Terence Stephenson, Sabine E Hofer, Siri Fredheim, Siv J Kummernes, Nicole Foster, Lena Hanberger, Rakesh Amin, Birgit Rami-Merhar, Anders Johansen, Knut Dahl-Jørgensen, Mark Clements, Ragnar Hanas

International studies on childhood type 1 diabetes (T1D) have focused on whole-country mean HbA1c levels, thereby concealing potential variations within countries. We aimed to explore the variations in HbA1c 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, US, 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 HbA1c 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 HbA1c (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 HbA1c (61-62 mmol/mol [7.7-7.8%]) but showed the largest center variations (ICC ∼15%). Centers in England, Wales, and the US 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 (P value <0.001). Across all countries, children attending centers with more variable glycemic results had higher HbA1c levels (5.6 mmol/mol [0.5%] per 5 mmol/mol [0.5%] increase in center HbA1c SD). At similar average levels of HbA1c, 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.