Comparison of tissue transglutaminase-specific antibody assays with established antibody measurements for coeliac disease

Tissue transglutaminase C has recently been identified as one of the autoan tigens of endomysial antibodies found in coeliac disease. In this study we have cloned the human autoantigen and developed immunoassays measuring anti bodies to transglutaminase in order to compare their diagnostic performance to that of established markers of the disease. A radiobinding assay using in vitro transcribed and translated S-35-methionine-labelled transglutamina se detected Ige antibodies in 110 and IgA antibodies in 109 of 112 patients at diagnosis of coeliac disease and in three and four of 92 control subjec ts, respectively. A radiobinding assay measuring both IgG and IgA transglut aminase antibodies identified 111 (99.1%) of the patients and 4 (4.3%) cont rol subjects. Concordance of this assay with the IgA endomysial antibody te st was found in 108 patients and 89 control subjects: two patients who had IgA deficiency and a third patient without IgA deficiency were only detecte d in the radiobinding assay; one patient had weak IgA endomysial antibodies only, and three of the control subjects with weak transglutaminase antibod ies by radiobinding assay were undetectable in the IgA endomysial antibody assay. IgA and IgG ELISA using guinea pig transglutaminase and commercial E LISA measuring anti-gliadin antibodies had lower sensitivity and specificit y than the radiobinding assays or the IgA endomysial antibody assay. This s tudy confirms tissue transglutaminase C as a major autoantigen in coeliac d isease and describes novel radiobinding assays for large scale testing to i dentify cases of coeliac disease. (C) 1999 Academic Press.