, Volume 37, Issue 4, pp 344–350 | Cite as

A novel radioligand binding assay to determine diagnostic accuracy of isoform-specific glutamic acid decarboxylase antibodies in childhood IDDM

  • C. E. Grubin
  • T. Daniels
  • B. Toivola
  • M. Landin-Olsson
  • W. A. Hagopian
  • L. Li
  • A. E. Karlsen
  • E. Boel
  • B. Michelsen
  • Å. Lernmark


Insulin-dependent diabetes mellitus (IDDM) is associated with autoreactivity against GAD but the diagnostic sensitivity (positivity in disease) and specificity (negativity in health) of isoform-specific GAD antibodies have yet to be defined in assay systems suitable for screening large number of samples. One set of IDDM patient (n=10) and control (n=50) standard sera were used to develop quantitative antibody assays with in vitro synthesized recombinant 35S-methionine-labelled GAD65 and GAD67, respectively, and protein A-Sepharose to separate free from antibody-bound ligand. Binding levels were not normally distributed (p<0.0001) and therefore, the diagnostic accuracy of GAD antibodies was analysed by the ROC plots in population-based, consecutively-diagnosed, recent onset, 0–14 year-old patients (n=105), and matched, healthy control subjects (n=157). The ROC plots showed that the diagnostic sensitivity of GAD65 antibodies was 77% and the specificity 92% compared with 8% and 98%, respectively for GAD67 antibodies. In the IDDM sera, GAD65 and GAD67 antibodies were concordant in 7% (6 of 81) and GAD65 antibodies and ICA in 89% (72 of 81) without a correlation between the autoantibody levels. Autoantibodies to recombinant human islet GAD65 are specific and sensitive markers for childhood IDDM in this immunoassay with in vitro synthesized 35S-methioninelabelled recombinant GAD.

Key words

Glutamic acid decarboxylase receiver-operating characteristic plot diagnostic accuracy islet cell antibodies autoimmunity diabetes mellitus 



insulin-dependent diabetes mellitus


glutamic acid decarboxylase


receiver-operating characteristic


islet cell antibodies


Juvenile Diabetes Foundation


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Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • C. E. Grubin
    • 1
  • T. Daniels
    • 1
  • B. Toivola
    • 2
  • M. Landin-Olsson
    • 3
  • W. A. Hagopian
    • 1
  • L. Li
    • 1
  • A. E. Karlsen
    • 4
  • E. Boel
    • 5
  • B. Michelsen
    • 4
  • Å. Lernmark
    • 1
    • 6
  1. 1.Department of MedicineUniversity of WashingtonSeattleUSA
  2. 2.Department of Laboratory MedicineUniversity of WashingtonSeattleUSA
  3. 3.Department of MedicineUniversity of LundLundSweden
  4. 4.Hagedorn Research InstituteGentofteDenmark
  5. 5.Novo Nordisk A/SBagsvaerdDenmark
  6. 6.Karolinska Institute, Department of EndocrinologyKarolinska Hospital, L1:02StockholmSweden

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