Evaluation of ICA512As in combination with other islet cell autoantibodies at the onset of IDDM.
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.


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.
Feeney
S J
SJ
Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
Myers
M A
MA
Mackay
I R
IR
Zimmet
P Z
PZ
Howard
N
N
Verge
C F
CF
Rowley
M J
MJ
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D017668:Age of Onset; D001315:Australia; D001323:Autoantibodies / Q000097:blood*; D001324:Autoantigens; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003922:Diabetes Mellitus, Type 1 / Q000097:blood / Q000276:immunology*; D005260:Female; D005968:Glutamate Decarboxylase / Q000097:blood / Q000276:immunology; D006801:Humans; D007223:Infant; D007330:Insulin Antibodies / Q000097:blood / Q000276:immunology; D007515:Islets of Langerhans / Q000276:immunology*; D008297:Male; D008565:Membrane Proteins / Q000097:blood / Q000276:immunology*; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases / Q000097:blood / Q000276:immunology*; D015531:Radioimmunoprecipitation Assay; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D012016:Reference Values; D012680:Sensitivity and Specificity
D001323:Autoantibodies; D001324:Autoantigens; D007330:Insulin Antibodies; D008565:Membrane Proteins; C024211:islet cell antibody; C516862:PTPRN protein, human; D054562:Protein Tyrosine Phosphatase, Non-Receptor Type 1; D017027:Protein Tyrosine Phosphatases; D054635:Receptor-Like Protein Tyrosine Phosphatases, Class 8; D005968:Glutamate Decarboxylase