(CSEMP064) THE ROLE OF ANTI-GLUTAMIC ACID DECARBOXYLASE ANTIBODIES IN PATIENT CARE: IDENTIFYING CURRENT PRACTICE AND FUTURE POTENTIAL FOR PATIENTS WITH DIABETES

Abstract: Background
Diabetes mellitus (DM) encompasses Type 2 DM (T2DM), characterized by insulin resistance, Type 1 DM (T1DM) and Latent Autoimmune Diabetes in Adults (LADA) - both of which are characterized by autoimmunity. Anti-glutamic acid decarboxylase (anti-GAD) antibodies are positive in up to ~ 80% of newly diagnosed T1DM patients and may also be positive in patients with LADA. To improve clarity on the indications to test for anti-GAD antibodies in DM patients, we are studying the current clinical utility of these antibodies and how their results impact patient care.

Methods
We are performing a retrospective chart review for patients who had anti-GAD antibodies ordered between 1 January 2020 and 31 December 2021. Data collected include the titre of anti-GAD antibodies, patients’ age, sex, type of DM, and the specialty of the ordering physician. We categorized patients based on the clinical context in which the anti-GAD antibodies were ordered. Furthermore, we documented patient cases where the anti-GAD antibodies were instrumental in changing the patient’s diagnosis for type of DM from T2DM to T1DM or LADA.

Results
Interim results (January 2020 – June 2021) show that the top reason (39% of cases) for ordering anti-GAD antibodies is to detect possible autoimmunity in T2DM patients who develop diabetic ketoacidosis (DKA) or other signs of insulin insufficiency, or who have inadequate glycemic control on non-insulin forms of anti-hyperglycemic medications. Anti-GAD antibodies are also ordered in patients with a first presentation of DKA / signs or symptoms of insulin insufficiency, and for confirmation in T1DM patients. In 22 out of 243 patients with diabetes (9.1%), a positive anti-GAD antibody result led to a change in diagnosis from T2DM to LADA.

Conclusions
Anti-GAD antibodies’ positivity can support a change in diagnosis from T2DM to LADA, which has substantial impact on patient care. More in-depth understanding of anti-GAD antibodies will clarify their role in future guidelines for DM diagnosis.