Impact of changes in gestational diabetes mellitus diagnostic criteria during the COVID-19 pandemic

Background/Aims: During the COVID-19 pandemic, the Health Service Executive (HSE) and Royal College of Obstetricians and Gynaecologists (RCOG) recommended fasting and random plasma glucose (FPG/RPG) alongside glycated haemoglobin (HbA_1c) to replace the oral glucose tolerance test (OGTT) for diagnosing Gestational Diabetes Mellitus (GDM). Methods: The study compared testing patterns and diagnostic rates for GDM before and after implementing the RCOG guidelines (01/05/2020) in pregnancies beginning 01/11/2018 to 31/03/2021. Trends were inspected using Cochrane-Armitage tests. Differences between General Practice (GP) and Secondary Care (SCare) were assessed by chi-square analysis. A significance level of p < 0.05 was used for all analyses. Information on maternal and pregnancy characteristics was accessed where available. Results: Data indicated a significant reduction in OGTTs requested by GPs and SCare. Conversely, HbA_1c, FPG and RPG test requests increased significantly in both locations. The overall GDM positivity rate increased significantly from 7.4% to 22.0% in GP and 16.9% to 39.0% in SCare following RCOG guideline implementation. Conclusions: The RCOG guidelines appear to have been well adopted by GPs and SCare, with greater adherence in SCare. Using FPG, RPG and HbA_1c to a greater extent than the OGTT corresponded with increased GDM diagnostic rates. Given the difficulties with interpreting HbA_1c in pregnancy, its routine use in diagnosing GDM requires further careful consideration. Relaying changes in diagnostic protocol during pandemics requires strong communication with all requesting clinicians, including GPs. Comparisons between GP and SCare indicated significant differences in test-requesting practices and GDM positivity rates.