The development of a World Health Organisation international standard for islet cell antibodies: the aims and design of an international collaborative study

Islet cell antibodies (ICA) are a specific marker for Type 1 (insulin-depen dent) diabetes mellitus. ICA are found in the serum of over 80% of newly di agnosed patients and the levels of ICA are directly of prognostic value. St andardisation of ICA and the uniform reporting of ICA levels in internation al units is critical to preclinical/clinical research and the development o f assays for ICA as diagnostics, in particular for the differential diagnos is of late onset Type 1 and Type 2 diabetes. Proficiency studies carried ou t by the Immunology of Diabetes Workshops on Standardization have clearly s hown that a single reference material, serum sample 673, obtained by Dr J. Ludvigsson, has significantly reduced inter- and intra-assay variability in the reporting of ICA levels. Nevertheless, this material is a frozen serum of limited shelf-life and is difficult to distribute on a worldwide and ro utine basis. Therefore, the Immunology of Diabetes Workshop Standardization Committee and the Juvenile Diabetes Foundation International requested tha t the National Institute for Biological Standards and Control (NIBSC) organ ise an international collaborative study to compare the activities of lyoph ilised, stable ICA preparations. In addition, the purpose was to investigat e if sample 673 could also serve as a standard for GAD65 and IA-2 antibodie s. Twenty participants in eight: countries have been recruited to the study . Copyright (C) 1999 John Wiley & Sons, Ltd.