Diabetes Care, Vol 20, Issue 9 1403-1407, Copyright © 1997 by American Diabetes Association
Evaluation of ICA512As in combination with other islet cell autoantibodies at the onset of IDDM
SJ Feeney, MA Myers, IR Mackay, PZ Zimmet, N Howard, CF Verge and MJ Rowley
Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
OBJECTIVE: The ICA512 pancreatic islet autoantigen is a putative tyrosine
phosphatase that is co-identified with the earlier described 40-kDa
autoantigen. We report the frequency of autoantibodies to islet cell
antigen 512 (ICA512As) in recent-onset IDDM and compare this with other
islet cell autoantibodies, including those to GAD (GADAs), insulin (IAAs),
and islet cell cytoplasm (ICAs) identified by immunofluorescence. RESEARCH
DESIGN AND METHODS: Sera from 232 children aged between 9 months and 14.9
years collected within 14 days of diagnosis were tested for ICA512As by a
radioimmunoprecipitation assay. The results were compared with previously
reported data for GADAs (n = 232), IAAs (n = 167), and ICAs (n = 230).
RESULTS: The frequency of a positive result for ICA512As in children with
newly diagnosed IDDM was 60%. The frequency was greater for children with
an age of onset between 5 and 10 years (69%) than for children aged < 5
years (49%) and aged between 10 and 15 years (56%). The frequencies for
other autoantibody reactivities were 69% for GADAs, 65% for IAAs, and 70%
for ICAs. A combination of positive results for ICA512As, GADAs, and IAAs
gave a sensitivity for the diagnosis of childhood IDDM of 95%, which was
not significantly increased by a positive result for ICAs (96%).
CONCLUSIONS: Our results further establish that positivity in a combination
of tests is more valuable for the prediction of IDDM than a result for any
single autoantibody and that the age of the patient should be considered
when selecting the combination of tests to use.