Autoantibodies to glutamic acid decarboxylase (GAD) are frequent at or before the onset of insulin-dependent diabetes mellitus (IDDM). We have developed a simple, reproducible, and quantitative immunoprecipitation radioligand assay using as antigen in vitro transcribed and translated [35S]methionine-labeled human islet GAD65. By using this assay, 77% (77 of 100) of serum samples from recent-onset IDDM patients were positive for GAD65 antibodies compared with 4% (4 of 100) of serum samples from healthy control subjects. In competition analysis with unlabeled purified recombinant human islet GAD65, binding to tracer was inhibited in 74% (74 of 100) of the GAD65-positive IDDM serum samples compared with 2% of the control samples. The levels of GAD antibodies expressed as an index value relative to a standard serum, analyzed with or without competition, were almost identical (r = 0.991). The intra- and interassay variations of a positive control serum sample were 2.9 and 7.6%, respectively (n = 4). The frequency of GAD antibodies was significantly higher with IDDM onset before the age of 30 (80%, 59 of 74) than after the age of 30 (48%, 10 of 21) (P < 0.01). The prevalence of islet cell antibodies showed a similar pattern relative to age at onset. Because simultaneous occurrences of multiple autoimmune phenomena are common, we analyzed sera from patients with other autoimmune diseases. The frequency of GAD antibodies in sera positive for DNA autoantibodies (8% [2 of 25] and 4% [1 of 25] in competition analysis) or rheuma factor autoantibodies [12% (4 of 35) and 3% (1 of 35) in competition analysis] was not different from that in control samples. In contrast, in sera positive for ribonucleoprotein antibodies the frequency of GAD antibodies was significantly increased (73% [51 of 70] and 10% [7 of 70] in competition analysis [P < 0.025]). In conclusion, even large numbers of serum samples can now be tested for GAD65 antibodies in a relatively short time, allowing screening of individuals without a family history of IDDM for the presence of this marker.
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Original Articles|
March 01 1994
Detection of GAD65 Antibodies in Diabetes and Other Autoimmune Diseases Using a Simple Radioligand Assay
Jacob S Petersen;
Jacob S Petersen
Hagedom Research Institute
Gentofte, Denmark
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Kim R Hejnaæs;
Kim R Hejnaæs
Novo-Nordisk A/S
Bagsvaerd, Denmark
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Alister Moody;
Alister Moody
Novo-Nordisk A/S
Bagsvaerd, Denmark
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Allan E Karlsen;
Allan E Karlsen
Hagedom Research Institute
Gentofte, Denmark
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Michael O Marshall;
Michael O Marshall
Novo-Nordisk A/S
Bagsvaerd, Denmark
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Mimi Høier-Madsen;
Mimi Høier-Madsen
State Serum Institute
Copenhagen, Denmark
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Esper Boel;
Esper Boel
Novo-Nordisk A/S
Bagsvaerd, Denmark
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Birgitte K Michelsen;
Birgitte K Michelsen
Hagedom Research Institute
Gentofte, Denmark
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Thomas Dyrberg
Thomas Dyrberg
Novo-Nordisk A/S
Bagsvaerd, Denmark
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Address correspondence and reprint requests to Dr. Thomas Dyrberg, Novo-Nordisk A/S, Novo Alle, DK-2880 Bagsvaerd, Denmark.
Diabetes 1994;43(3):459–467
Article history
Received:
August 10 1993
Revision Received:
November 02 1993
Accepted:
November 02 1993
PubMed:
8314020
Citation
Jacob S Petersen, Kim R Hejnaæs, Alister Moody, Allan E Karlsen, Michael O Marshall, Mimi Høier-Madsen, Esper Boel, Birgitte K Michelsen, Thomas Dyrberg; Detection of GAD65 Antibodies in Diabetes and Other Autoimmune Diseases Using a Simple Radioligand Assay. Diabetes 1 March 1994; 43 (3): 459–467. https://doi.org/10.2337/diab.43.3.459
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