The potential of anti-glutamic acid decarboxylase antibodies to support a diagnosis of autoimmune diabetes mellitus

Maryah Liepert; Shamayel Alhaqqan; Alaa Husain; Heather Lochnan; Ronald A Booth; Julie Shaw; Cathy J Sun

doi:10.1016/j.clinbiochem.2024.110842

The potential of anti-glutamic acid decarboxylase antibodies to support a diagnosis of autoimmune diabetes mellitus

Clin Biochem. 2024 Nov 17:135:110842. doi: 10.1016/j.clinbiochem.2024.110842. Online ahead of print.

Authors

Maryah Liepert¹, Shamayel Alhaqqan², Alaa Husain³, Heather Lochnan⁴, Ronald A Booth⁵, Julie Shaw⁶, Cathy J Sun⁷

Affiliations

¹ Division of General Internal Medicine, Department of Medicine, The Ottawa Hospital, University of Ottawa, 501 Smyth Rd, Ottawa, Ontario, K1H 8L6, Canada. Electronic address: mliepert@toh.ca.
² Division of General Internal Medicine, Department of Medicine, The Ottawa Hospital, University of Ottawa, 501 Smyth Rd, Ottawa, Ontario, K1H 8L6, Canada. Electronic address: salhaqqan@toh.ca.
³ Division of Endocrinology and Metabolism, Department of Medicine, The Ottawa Hospital, University of Ottawa, 1967 Riverside Drive, Ottawa, Ontario, K1H 7W9, Canada. Electronic address: alhusain@toh.ca.
⁴ Division of Endocrinology and Metabolism, Department of Medicine, The Ottawa Hospital, University of Ottawa, Ottawa Hospital Research Institute, 1967 Riverside Drive 4th Floor Endocrinology, Ottawa, Ontario, K1H 7W9, Canada. Electronic address: hlochnan@toh.ca.
⁵ Division of Biochemistry, Department of Pathology and Laboratory Medicine, The Ottawa Hospital, 501 Smyth Rd, Ottawa, Ontario, K1H 8L6, Canada. Electronic address: rbooth@uottawa.ca.
⁶ Division of Biochemistry, Department of Pathology and Laboratory Medicine, The Ottawa Hospital, 501 Smyth Rd, Ottawa, Ontario, K1H 8L6, Canada. Electronic address: julshaw@eorla.ca.
⁷ Division of Endocrinology and Metabolism, Department of Medicine, The Ottawa Hospital, University of Ottawa, Ottawa Hospital Research Institute, 1967 Riverside Drive 4th Floor Endocrinology, Ottawa, Ontario, K1H 7W9, Canada. Electronic address: csun@toh.ca.

PMID: 39551460
DOI: 10.1016/j.clinbiochem.2024.110842

Abstract

Objective: Anti-glutamic acid decarboxylase (anti-GAD) antibodies are a frequently used diagnostic marker for autoimmune forms of diabetes mellitus (DM), namely, type 1 diabetes mellitus (T1DM) and latent autoimmune diabetes in adults (LADA). We sought to provide insight into a unique diagnostic application of anti-GAD antibodies in patients potentially misdiagnosed with type 2 diabetes mellitus (T2DM).

Methods: We present a case series of patients who had a change in diagnosis from T2DM to autoimmune DM that was supported by positive anti-GAD antibodies. Patients were identified via a retrospective chart review of all anti-GAD antibodies tests ordered between 1 January 2020 and 31 December 2021 at a tertiary care academic hospital.

Results: Of the 23 patients with previous diagnosis of T2DM, positive anti-GAD antibodies supported the clinician's decision to change the diagnosis to autoimmune DM. The prominent clinical reasons for ordering anti-GAD antibodies in patients previously diagnosed as T2DM were patient presentation with diabetic ketoacidosis, features of insulin insufficiency, inadequate effect of oral diabetes mellitus medications, young age at diagnosis, and a family history of autoimmune conditions.

Conclusion: Anti-GAD antibodies' positivity can support a change in diagnosis from T2DM to autoimmune DM, which has substantial impact on patient care. Timely and reliable clinical laboratory reporting of anti-GAD antibodies is highly recommended.

Keywords: Anti-glutamic acid decarboxylase antibodies; Autoimmune diabetes mellitus; Latent-autoimmune diabetes in adults; Type 1 diabetes mellitus; Type 2 diabetes mellitus.

Publication types

Case Reports