Serologic screening for celiac disease in children: a comparison between established assays and tests with deamidated gliadin-derived peptides plus conjugates for both IgA and IgG antibodies

Selection of patients for diagnostic biopsy concerning celiac disease (CD) is mainly guided by the results with serological screening tests like anti-tissue-transglutaminase (tTG), anti-endomysium (EmA) and anti-gliadin (AGA) IgA. New tests using deamidated gliadin-derived peptides (DGP) including both IgA and IgG antibodies have been developed, to cover the IgA-deficient sera. In addition, a combined IgA and IgG DGP test, with or without human erythrocyte-derived tTG, offers possible advantages. In order to explore the screening accuracy of the new combination tests sera from 167 children below 3 years of age were assayed. Biopsy had been taken in connection with serology in 32 of these children, 24 with histopathological CD. The results with the DGP and the combined test were congruent with the IgA antibody tests for tTG, EmA and AGA, all identifying 21 of 24 of the CD cases. Two of the CD patients were AGA-IgA positive only (2/24), while 2 of 24 sera were AGA-IgA negative but positive in all the other tests. These results raises the question whether the modifications of the gliadin antigen not only decrease false positivity but also give more false-negative results, a major drawback for a screening test for an important disease. Further studies have to be undertaken to explore this. Our results also stress that serologic screening of CD in children cannot be based on one test only.