Determination of anti GAD65 autoantibodies with an ELISA before and after standardization with the new international reference serum.

The serum of a stiff-man syndrome patient was declared international GAD reference standard at the "1st GAD Antibody Workshop" held at the "12th International Immunology and Diabetes Workshop" in Orlando, Florida, USA 1993. A comparative study was performed with 123 diabetic and non-diabetic patients to evaluate whether standardization of this reference serum had changed the properties of a commercially available ELISA assay. All samples classified positive with the old test were confirmed with the new assay. Four additional samples with high "normal" values became positive with the new test. One of them was a control person having a family history of diabetes and genetic loci DR4/DR11. These findings might implicate a higher risk for the development of IDDM. The new standardization and adaptation of the ELISA seems to have influenced the sensitivity of the test positively.