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Evaluation of a novel radioimmunoassay using125I-labelled human recombinant GAD65 for the determination of glutamic acid decarboxylase (GAD65) autoantibodies

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International Journal of Clinical and Laboratory Research

Abstract

Autoantibodies to the islet cell 65-kilodalton isoform of glutamic acid decarboxylase (GAD65) are present in most patients with type 1 diabetes mellitus years before the clinical manifestation of the disease. GAD65 autoantibodies are also present in a subset of patients with type 2 diabetes who frequently become insulin dependent. In the present study, we evaluated a new, commercially available radioimmunoprecipitation assay for measuring GAD65 autoantibodies using125I-labelled human recombinant GAD65. Results obtained with this assay were compared with those obtained by a reference assay based on35S-labelled recombinant GAD65. Analyses were performed on 67 patients with type 1 diabetes, 350 with type 2 diabetes, and 150 apparently healthy individuals. An excellent agreement was found between the results obtained by the125I-GAD65 assay and those obtained by the reference method. The receiver operating characteristic (ROC) curve analysis was used to evaluate the sensitivity and specificity of the two assays. The sensitivity of each assay was determined from the results of the 67 type 1 patients, while the specificity was based on the 150 healthy individuals. Based on the ROC curves, the two assays appeared identical, with a sensitivity of 84% and a clinical specificity of 98%. In conclusion, based on our results, this simple, one-step centrifugation, high-capacity125I-GAD65 assay has the same sensitivity and specificity as the reference assay and is highly suitable to detect GAD65 autoantibodies in human samples.

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Authors and Affiliations

  1. Department of Medicine, University of Washington, Seattle, Washington, USA

    S. M. Marcovina, J. P. Palmer & Å. Lernmark

  2. Department of Medicine, Lund University Hospital, Lund, Sweden

    M. Landin-Olsson

  3. Diamyd Diagnostics, Stockholm, Sweden

    A. Essen-Möller

Authors
  1. S. M. Marcovina
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  2. M. Landin-Olsson
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  3. A. Essen-Möller
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  4. J. P. Palmer
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  5. Å. Lernmark
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Marcovina, S.M., Landin-Olsson, M., Essen-Möller, A. et al. Evaluation of a novel radioimmunoassay using125I-labelled human recombinant GAD65 for the determination of glutamic acid decarboxylase (GAD65) autoantibodies. Int J Clin Lab Res 30, 21–26 (2000). https://doi.org/10.1007/s005990070029

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  • DOI: https://doi.org/10.1007/s005990070029

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