Journal of Diabetes Investigation (Mar 2020)

Clinical and genetic characteristics of people with type 1 diabetes who have discrepancies in titers of anti‐glutamic acid decarboxylase antibody measured by radioimmunoassay and enzyme‐linked immunosorbent assay

  • Satoshi Takagi,
  • Junnosuke Miura,
  • Sari Hoshina,
  • Yasuko Uchigata,
  • Tetsuya Babazono

DOI
https://doi.org/10.1111/jdi.13111
Journal volume & issue
Vol. 11, no. 2
pp. 356 – 362

Abstract

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Abstract Aims/Introduction The aim of the present study was to compare the clinical and genetic characteristics between people with type 1 diabetes who were positive and negative for autoantibodies against glutamic acid decarboxylase (GADA) measured by enzyme‐linked immunosorbent assay (ELISA) with low‐titer GADA measured by radioimmunoassay. Materials and Methods Among Japanese people with type 1 diabetes in whom GADA were measured by both ELISA and radioimmunoassay, those who had low titers of GADA measured by radioimmunoassay (1.5–10 U/mL), regardless of positivity for GADA measured by ELISA, were studied. There were 65 participants with acute‐onset type 1 diabetes and 30 participants with slowly progressive insulin‐dependent diabetes mellitus. Clinical characteristics and human leukocyte antigen types were compared in ELISA‐positive (≥5 U/mL) and ELISA‐negative participants. Endogenous insulin secretion was evaluated by C‐peptide index. Results Among participants with slowly progressive insulin‐dependent diabetes mellitus, postprandial C‐peptide index was significantly higher in ELISA‐negative participants than in ELISA‐positive participants (r = 0.619, P = 0.002). Among 52 participants whose human leukocyte antigen typing was carried out, all of the participants with slowly progressive insulin‐dependent diabetes mellitus who had DRB1*09:01 were positive by GADA‐ELISA (P = 0.021). In acute‐onset type 1 diabetes participants, there were no significant differences for the C‐peptide index and human leukocyte antigen genotypes. Conclusions The difference in the positivity for GADA‐ELISA might reflect cytotoxicity toward pancreatic β‐cells and preservation of endogenous insulin secretion in people with slowly progressive insulin‐dependent diabetes mellitus. We also suggest that the difference in the GADA‐ELISA‐specific epitope depends on the human leukocyte antigen genotype.

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