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- Agardh, Daniel, et al.
(author)
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Calcium activation of tissue transglutaminase in radioligand binding and enzyme-linked autoantibody immunoassays in childhood celiac disease.
- 2005
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In: Clinica Chimica Acta. - : Elsevier BV. - 0009-8981. ; 358:1-2, s. 95-103
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Journal article (peer-reviewed)abstract
- Background Conflicting data have been published concerning the effect of calcium on binding of autoantibodies to tissue transglutaminase (tTG) in celiac disease (CD). Methods IgA-tTG and IgG-tTG were measured with radioligand binding assays (RBA) using human recombinant (hr) 35S-tTG produced in lysate of rabbit reticulocytes and with guinea pig (gp) tTG ELISA in 51 CD children (median: 5.7 years) and 35 controls (median: 2.2 years). Assays were performed with and without calcium. Results In hr-tTG RBA, IgA-tTG levels remained unchanged after calcium detecting 50/51 CD children and 1/35 controls (p < 0.0001). IgG-tTG levels decreased with calcium (p < 0.0001) in CD children and detected 48/51 with and 49/51 without calcium as compared to 1/35 controls (p < 0.0001). In gp-tTG ELISA, levels increased with calcium (p < 0.0001) making it possible to detect an additional three to a total of 50/51 with IgA-tTG and 13 to 39/51 CD children with IgG-tTG compared to 4/35 and 8/35 controls (respectively, p < 0.0001). Rabbit reticulocytes displayed calcium-dependent tTG activity. Conclusions Calcium increased binding of IgA-tTG and IgG-tTG in the ELISA test. The reverse effect observed in RBA may be explained by competitive binding between calcium activated native rabbit reticulocyte tTG and hr 35S-tTG. tTG autoantibody assays may need taking calcium into account for accurate diagnostic sensitivity and specificity for CD.
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| 2. |
- Dahlbom, Ingrid, et al.
(author)
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Protein A and protein G ELISA for the detection of IgG autoantibodies against tissue transglutaminase in childhood celiac disease
- 2008
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In: Clinica Chimica Acta. - : Elsevier BV. - 0009-8981 .- 1873-3492. ; 395:1-2, s. 72-6
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Journal article (peer-reviewed)abstract
- Objectives: 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.
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| 3. |
- Teesalu, Kaupo, et al.
(author)
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A modified ELISA for improved detection of IgA, IgG, and IgM anti-tissue transglutaminase antibodies in celiac disease
- 2009
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In: Clinica Chimica Acta. - : Elsevier BV. - 0009-8981. ; 403:1-2, s. 37-41
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Journal article (peer-reviewed)abstract
- Background: Serum IgA antibodies against tissue transglutaminase (tTG) are reliable markers for celiac disease (CD), still the diagnostic performance of anti-tTG immunoassays can be improved. A novel ELISA, using fibronectin (FN) as tTG binding protein, was evaluated for the detection of anti-tTG antibodies in CD. Methods: Sera from 173 children with untreated CD and 97 controls were analyzed for IgA, IgG, and IgM anti-tTG antibodies with ELISA using human recombinant tTG with or without FN. Results: The areas under the ROC (receiver operating characteristic) curves were significantly higher for FN/tTG ELISA compared to tTG ELISA for IgG (0.930 versus 0.809; p < 0.001) and IgM (0.850 versus 0.811; p = 0.019), but not for IgA (0.977 versus 0.970; p = 0.356), respectively. At the fixed diagnostic specificity (100% for IgA and IgM, 99% for IgG), the sensitivity of all three FN/tTG ELISA (92.5% for IgA, 60.7% for IgG, 50.3% for IgM) exceeded those obtained in tTG ELISA (89.0% for IgA, 48.6% for IgG, 38.7% for IgM; p < 0.05). The combined use of IgA- and IgG-FN/tTG ELISA resulted in 95.4% sensitivity and 99.0% specificity for CD. Conclusions: Using FN to bind tTG improves the diagnostic performance of solid phase anti-tTG antibody assays for childhood CD. (C) 2009 Elsevier B.V. All rights reserved.
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