Abstract
Aim: Making the correct diagnosis of diabetes type determines the patient's clinical management pathway. Diabetes-related antibodies are useful diagnostic tests, as they are typically present in Type 1 diabetes but absent in other forms. This study aimed to determine where these laboratory antibody tests were ordered (eg, primary care vs secondary care) and to describe the positivity rates.
Methods: A retrospective clinical audit was conducted over 2 years (January 2023 to December 2024) in the Canterbury region of Aotearoa New Zealand. The audit included all laboratory requests for glutamic acid decarboxylase-65 (GAD65), insulinoma antigen 2 (IA2), and zinc transporter 8 (ZnT8) antibodies submitted through Canterbury Health Laboratories. Unique patients were identified through their National Health Index number.
Results: A total of 1505 tests were requested on 813 unique patients. Although most test requests for children and young adults were initiated by secondary care, overall, most requests came from primary care. In older patients aged 35+ years, the percentage positivity was broadly similar between primary and secondary care: primary care tested 361 patients and 17% were positive; secondary care tested 187 patients and 21% were positive.
Discussion: Most diabetes-related antibody tests were ordered by primary care, and New Zealand testing guidance should reflect this primary care perspective. This shift in testing patterns towards primary care supports the need for updated clinical guidelines that reflect the diagnostic responsibilities now assumed by general practice.