Protein A and protein G ELISA for the detection of IgG autoantibodies against tissue transglutaminase in childhood celiac disease.
OBJECTIVE
To investigate if the detection of celiac disease (CD) in children was improved by using alternative conjugates for assessment of tissue transglutaminase (tTG) autoantibodies.


METHODS
Serum samples from 108 biopsy confirmed CD children and 42 control subjects were investigated for the presence of autoantibodies with tTG coated microplates using protein A (PA), protein G (PG), anti-IgG, or anti-IgA as conjugates.


RESULTS
Of the 108 CD children, 86 (80%) were IgG-tTG positive, 91 (84%) were positive with the PA-conjugate, 94 (87%) were positive with the PG-conjugate, and 103 (95%) were IgA-tTG positive. Among the 42 controls, 4 (10%) were IgG-tTG positive, 5 (12%) were positive with both the PA- and PG conjugates, whereas 3 (7%) were IgA-tTG positive. Compared with IgG-tTG the concordance was 93% for PA and 95% for PG, with a positive correlation between antibody levels (r=0.967 and r=0.975, p<0.0001). All but one CD child were found positive by combining IgG-tTG and IgA-tTG detection.


CONCLUSIONS
The sensitivity of IgG-tTG detection with ELISA increased by protein A or protein G conjugates, whereas the specificity was reduced as compared with anti-IgG conjugate. The combined measurement of IgA-tTG and IgG-tTG still seems to be the optimal procedure when screening children for CD.
Department of Genetics and Pathology, Uppsala University, Uppsala, Sweden. ingrid.dahlborn@kbh.uu.se
Ingrid
I
Dahlbom
Daniel
D
Agardh
Tony
T
Hansson
D000293:Adolescent; D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D002446:Celiac Disease / Q000097:blood* / Q000276:immunology; D002648:Child; D002675:Child, Preschool; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods; D005260:Female; D019204:GTP-Binding Proteins / Q000276:immunology*; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood*; D007223:Infant; D008297:Male; D009419:Nerve Tissue Proteins / Q000737:chemistry*; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013205:Staphylococcal Protein A / Q000737:chemistry*; D011503:Transglutaminases / Q000276:immunology*
D001323:Autoantibodies; C029152:G-substrate; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D009419:Nerve Tissue Proteins; D013205:Staphylococcal Protein A; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins