ABSTRACT AIMS/HYPOTHESIS: This study aimed to define the immunological parameters which could be used to identify patients with the distinct metabolic features of adult latent autoimmune diabetes.
Methods: Sera of 312 patients with short-term diabetes (duration < 5 years) over 35 years of age at diagnosis were screened for ICA, GAD- and IA2-Ab by antibody assays validated in workshops. The antibody status was correlated with age, BMI, residual beta-cell function, measured by fasting C-peptide, onset of diabetes-related complications and markers of the metabolic syndrome (hypertension and hyperlipidaemia).
Results: A total of 51 antibody positive patients were identified. These patients had lower fasting C-peptide and less neuropathy and hypertension compared with matched antibody-negative patients. However, only patients with two or more antibodies had reduced residual beta-cell function compared with antibody-negative or single antibody-positive (ICA or GAD-Ab only) patients. Patients with two or more antibodies were also leaner and had diabetes-related complications or hypertension less frequently than single antibody-positive or antibody negative-patients. IA2 antibody status did not substantially contribute to the diagnosis or differentiation of LADA patients.
Conclusion/interpretation: We concluded that the combination of ICA and GAD antibodies and high titre of GAD antibodies are characteristic of patients with insulin deficiency with the clinical features of Type I (insulin-dependent) diabetes mellitus (LADA-type 1). Single antibody positivity and low titre antibodies are markers for LADA-type 2 associated with the clinical and metabolic phenotype of Type II (non-insulin-dependent) diabetes patients.