Validation of Danish registry-cases of type 1 diabetes in women giving live birth using a clinical cohort as gold standard.

INTRODUCTION: The aim of this study was to validate type 1 diabetes in women giving live birth in the Danish national registries against a clinical cohort of confirmed cases (the Danish Diabetes Birth Registry [DDBR] cohort). METHODS: National registries including diagnosis codes, redeemed prescriptions and background data were combined. Three main algorithms were constructed to define type 1 diabetes in women giving live birth: (1) Any diabetes diagnosis registered before delivery and before age of 30, (2) a specific type 1 diabetes diagnosis registered before delivery regardless of maternal age and (3) a 'preexisting type 1 diabetes in pregnancy' diagnosis registered before delivery. In additional sub-algorithms, we added information on anti-diabetic medicine and gestational diabetes diagnosis. We calculated positive predictive value (PPV) and completeness using the DDBR cohort as gold standard. Since DDBR included between 75 and 93% of women with confirmed type 1 diabetes giving live birth, we used quantitative bias analysis to assess the potential impact of missing data on PPV and completeness. RESULTS: Main algorithm 2 had the highest PPV (77.4%) and shared the highest completeness (92.4%) with main algorithm 1. Information on anti-diabetic medicine and gestational diabetes increased PPV, on expense of completeness. All algorithms varied with PPV between 65.7 and 87.6% and completeness between 73.6 and 92.4%. The quantitative bias analysis indicated that PPV was underestimated, and completeness overestimated for all algorithms. For algorithm 2, corrected PPV was between 82.1 and 94.6% and corrected completeness between 84.7 and 91.2%. CONCLUSIONS: The Danish national registries can identify type 1 diabetes in women giving live birth with a reasonably high accuracy. The registries are a valuable source for future comparative outcome studies and may also be suitable for monitoring prevalence and incidence of type 1 diabetes in women giving live birth.

Academic Performance in Adolescents Born to Mothers With Gestational Diabetes-A National Danish Cohort Study.

CONTEXT: The prevalence of gestational diabetes mellitus (GDM) is increasing, and intrauterine hyperglycemia is suspected to affect offspring cognitive function. OBJECTIVE: We assessed academic performance by grade point average (GPA) in children aged 15 to 16 years at compulsory school graduation, comparing offspring exposed to GDM (O-GDM) with offspring from the background population (O-BP). METHODS: This register-based, cohort study comprised all singletons born in Denmark between 1994 and 2001 (O-GDM: n = 4286; O-BP: n = 501 045). Standardized and internationally comparable GPAs were compared in univariate and multivariable linear models. Main outcome measures included the adjusted mean difference in GPA. We also analyzed the probability of having a high GPA, a GPA below passing, and no GPA registered. RESULTS: O-GDM had a GPA of 6.29 (SD 2.52), whereas O-BP had a GPA of 6.78 (SD 2.50). The adjusted mean difference was -0.36 (95% CI, -0.44 to -0.29), corresponding to a Cohen's D of 0.14. O-GDM had a lower probability of obtaining a high GPA (adjusted odds ratio [aOR] 0.68; 95% CI, 0.59 to 0.79), while their risk of obtaining a GPA below passing was similar to O-BP (aOR 1.20; 95% CI, 0.96 to 1.50). O-GDM had a higher risk of not having a GPA registered (aOR 1.38; 95% CI, 1.24 to 1.53). CONCLUSION: Academic performance in O-GDM was marginally lower than in O-BP. However, this difference is unlikely to be of clinical importance.