Supplementary Material for: Numeracy skills and glycemic control in an observational, multi-centre, cross-sectional, and international study of children with Type 1 Diabetes

Introduction. This study examined the possible association between numeracy skills and glycemic outcomes in children with type 1 diabetes. Methods. The study used a cross-sectional design and collected data from 7 centres of the Hvidoere Study Group. HbA1c was measured centrally. Numeracy was assessed using the specific 5-item Diabetes Numeracy Test (DNT-5) and the international, general Wordless Mathematical Test (WMT). The HbA1c predictive multivariate generalised linear model was constructed using the adjusted R-squared index for model selection. Pearson's correlation coefficient was calculated between observed and predicted HbA1c levels in the training and testing datasets. Results. 306 adolescents aged 12-18 (mean age 14.96 ± 1.68) years and diabetes duration of 6.57 (± 3.75) participated in this study. Numeracy skills, as assessed by the WMT but not DNT 5, predicted the HbA1c levels after adjustment for sociodemographic and clinical factors. The correlation between observed and predicted HbA1c levels was consistent in both datasets and was 0.34 (N=155) and 0.37 (N=61) for the training and test datasets, respectively (p=0.412). The effect size for the WMT-based predictive model of HbA1c adjusted for clinical and socioeconomic factors was significantly higher (p<0.05) than the single-parameter-based model. Conclusion. Numeracy, as assessed by an international general math test, is a good predictor of HbA1c in children and adolescents with type 1 diabetes. The basic and short WMT is a potentially effective tool in personalised clinical pediatric diabetes practice. Therapy planning should consider adjusting therapy to compensate for lower numeracy skills and/or training to improve the patient’s numerical proficiency.