Islet autoantibody types mark differential clinical characteristics at diagnosis of pediatric type 1 diabetes

Characterisation of islet antibody-negative type 1 diabetes mellitus in Indian children

AIMS

Islet antibody-negative type 1 diabetes mellitus (T1DM) has not been well characterised. We determined the frequency of antibody-negative T1DM and compared it with antibody-positive T1DM in a cohort of north Indian children.

METHODS

In a multi-centre, prospective, observational study, 176 Indian children (age 1-18 years) were assessed within 2 weeks of diagnosis of T1DM. Antibodies against GAD65 (GADA), islet antigen-2 (IA-2A) and zinc transporter 8 (ZnT8A), were estimated using validated ELISA. HLA-DRB1, DQA1 and DQB1 alleles were studied by Luminex-based typing. Monogenic diabetes was determined by targeted next-generation sequencing using the Illumina platform.

RESULTS

After excluding 12 children with monogenic diabetes, GADA, IA-2A and ZnT8A were present in 124 (76%), 60 (37%) and 62 (38%) children, respectively, while 24 (15%) were negative for all antibodies. A single antibody (most frequently GADA) was present in 68 (41%) of children, while all three antibodies were found in 34 (21%). Islet antibody-negative T1DM (n = 24, 15%) did not differ from antibody-positive children in their clinical features, HbA1c or plasma C-peptide, both at onset or after 1 year follow-up (available in 62 children). The frequency of other organ-specific antibodies or high-risk HLA-DR and DQ alleles were also similar. Children with a single islet antibody did not differ from those with multiple antibodies.

CONCLUSIONS

The frequency of various islet-antibodies, in isolation and combination, differed considerably from studies among children of European descent with T1DM. Children with T1DM who were islet antibody-negative were indistinguishable from those who were antibody-positive.

Elevated Serum IgA at Onset of Type 1 Diabetes in Children

Background

Elevated serum IgA levels have been observed in various autoimmune conditions, including type 1 diabetes (T1D). However, whether children with T1D and elevated serum IgA have unique features has not been studied. We aimed to evaluate the prevalence and characteristics associated with elevated serum IgA at the onset of pediatric T1D.

Materials and Methods

We analyzed demographic, clinical, and laboratory data retrospectively collected from 631 racially diverse children (6 months-18 years of age) with T1D who had serum IgA levels measured within 90 days of T1D diagnosis. Univariable and multivariable logistic regression models were used to identify characteristics that were significantly associated with elevated versus normal IgA.

Results

Elevated serum IgA was present in 20.3% (128/631) of the children with newly diagnosed T1D. After adjusting for other variables, A1c level (p=0.029), positive insulin autoantibodies (IAA) (p=0.041), negative glutamic acid decarboxylase autoantibodies (GADA) (p=0.005) and Hispanic ethnicity (p  < 0.001) were significantly associated with elevated serum IgA. After adjustment for confounders, the odds of elevated serum IgA were significantly increased with positive IAA (OR 1.653, 95% CI 1.019-2.679), higher HbA1c (OR 1.132, 95% CI 1.014-1.268) and Hispanic ethnicity (OR 3.279, 95% CI 2.003-5.359) but decreased with GADA positivity (OR 0.474, 95% CI 0.281-0.805).

Conclusions

Elevated serum IgA is present in 20.3% of the children at T1D onset and is associated with specific demographic and clinical characteristics, suggesting a unique pathogenesis in a subset of individuals. Further studies are warranted to investigate the IgA response, its role in T1D pathogenesis, and whether these associations persist over time.

Glutamic Acid Decarboxylase and Tyrosine Phosphatase-Related Islet Antigen-2 Positivity among Children and Adolescents with Diabetes in Korea

Autoantibodies against glutamic acid decarboxylase (GADA), tyrosine phosphatase-related islet antigen 2 (IA2A), insulin (INSA), and islet cells (ICA) are critical for determining the type of diabetes and management strategy in new-onset diabetes mellitus (NODM), but there have been few reports of all diabetes-associated autoantibody (DAA) in Korea. We retrospectively analyzed 193 patients with NODM aged 0 to 18 years who were followed at two tertiary centers in Korea (2017 to 2021). Patients with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM) were 93 (48.2%) and 100 (51.8%), respectively. In T1DM patients, the DAA positivity rate was 94.6%; prevalence of GADA, IA2A, INSA, and ICA was 71.0%, 71.0%, 31.2%, and 10.8%, respectively; and IA2A added 10.7% point autoantibody positivity (83.9% for GADA+INSA+ICA and 94.6% for GADA+INSA+ICA+IA2A). Among the patients with T2DM, 12 (12.0%) were positive for DAA, and all were positive for INSA. These findings suggest that DAA at diagnosis, especially GADA and IA2A, is useful for classifying diabetes in Korean children and adolescents.