Objective: Latent autoimmune diabetes in adults (LADA) is characterized by positive islet-associated autoantibodies including glutamic acid decarboxylase antibody (GADA), and gradual decline in insulin secretion, progressing to insulin dependency. This cross-sectional study aimed to determine whether GADA by enzyme-linked immunosorbent assay (GADA-ELISA) titer of ≥180 U/mL could be associated with decline in β-cell function in participants with LADA.

Methods: Sixty-three participants with LADA were recruited and an association between insulin secretion capacity and disease duration was investigated. Insulin peptide-specific inflammatory immunoreactivity was investigated to determine the disease's activity.

Results: There was a significant inverse correlation between disease duration and C-peptide index in participants with GADA-ELISA titer of ≥180 U/mL (Spearman's r (rs) = -0.516, p < 0.01). The positivity rate of insulin peptide-specific inflammatory immunoreactivity was significantly higher in those with ≥180 U/mL than in those with <180 U/mL (p < 0.05). In participants with human leukocyte antigen (HLA)-DRB1*04:05, a significant inverse correlation was observed between disease duration and C-peptide index in those with ≥180 U/mL (rs = -0.751, p < 0.01).

Conclusions: GADA-ELISA titer of ≥180 U/mL, especially with HLA-DRB1*04:05, might reflect higher disease activity and may be associated with decline in β-cell function over time and future insulin dependency in LADA.