6445 Maturity onset diabetes of the young – are we misdiagnosing a subset of patients as type 1 diabetes mellitus and treating them suboptimally?

Objectives Maturity onset diabetes of the young (MODY), although rare, is the commonest form of monogenic diabetes, and could be misdiagnosed as type 1 diabetes by clinicians. It is thought to account for 1–2.5% of all cases of diabetes within the United Kingdom.1 We aimed to identify children within the diabetes service at Norfolk and Norwich University Hospitals NHS Foundation Trust (NNUH) who were mistakenly diagnosed as type 1 diabetes at presentation, and who in fact have a diagnosis of MODY. Methods A list of all patients under the paediatric diabetes service at NNUH in April 2022 was obtained. Results of glutamic acid decarboxylase antibodies (GAD) and islet cell antibodies (ICA) for these patients were checked. Patients with incomplete antibody testing had these requested, and forms were sent to their parents or carers asking them to have these completed. Amongst those with negative GAD and ICA, second line testing was requested for zinc transporter 8 antibodies (ZnT8) and islet antigen 2 antibodies (IA2). If these were also negative, insulin requirements, family history and c-peptide levels were reviewed and genetics were requested if appropriate to test for MODY. Results Blood test results from a total of 310 patients were analysed. Figure 1 summarises the results. 20 patients were excluded – one had type 2 diabetes, two had cystic fibrosis related diabetes, one had diabetes secondary to pancreatitis, and one had confirmed MODY. The rest moved out of area or transitioned to adult services whilst the project was ongoing. The other 290 were diagnosed with type 1 diabetes. 230/290 (79%) were positive for either ICA or GAD antibodies, or both. 29/290 (10%) were negative for both antibodies, and the rest have results outstanding. Amongst the 29 patients with negative ICA and GAD antibodies, 4/29 (1.4% of all patients) are also negative for ZnT8 and IA2 antibodies, 6/29 (2% of all patients) have one positive 2nd line antibody, and the rest have results outstanding. Of these four patients we have so far identified with four negative antibodies, one has had a negative gene panel for MODY, and the others have further investigations planned. Conclusion With a rate of MODY in the general population as it is, we would expect between 2–5 young people with MODY in our patient group. We currently have just one patient with confirmed MODY. This project is ongoing, but so far we have identified 3 potential patients with 4 negative antibodies who after further investigations may have their diagnosis revised, and if so, their treatment altered. References Nkonge, KM, Nkonge, DK 6:20.