Diagnostic performance of three serologic tests in childhood celiac disease.

BACKGROUND IgA- and IgG-antibodies against deamidated gliadin peptides (DGP) specifically bind the disease-inducing antigen and might be superior to transglutaminase type 2 (TG2) IgA in monitoring patients on a gluten-free diet (GFD). The aim of this study was to compare the performance of DGP-IgG and DGP-IgA with TG2-IgA of four manufacturers in pediatric celiac patients at diagnosis and during follow-up under a GFD. PATIENTS AND METHODS In total 411 sera of 91 IgA competent children with biopsy proven celiac disease were analyzed at diagnosis and during follow-up on a GFD. Ninety-eight children with normal duodenal histology served as controls. The tests (TheBindingSite, Euroimmun, Phadia, part of Thermo Fisher Scientific, INOVA) for detection of TG2-IgA, DGP-IgG and DGP-IgA were used according to the manufacturers' instructions. RESULTS Sensitivity to diagnose CD was high for TG2-IgA (100 %) and DGP-IgG (90 - 100 %), but lower for DGP-IgA (67 - 86 %). Specificity was high for all tests (97 - 100 %). The frequency of TG2-IgA titers > 10 × upper limit of normal at diagnosis ranged from 47 - 90 %. Under a GFD DGP-IgA became negative more rapidly than DGP-IgG and TG2-IgA. Non-adherence to GFD was best indicated by positive TG2-IgA. CONCLUSIONS Combined testing for TG2-IgA and DGP-IgG does not increase the detection rate of CD in IgA competent children compared to TG2-IgA only. There are significant differences with respect to proportions of celiac children with titers > 10 × ULN between the manufacturers. This calls for harmonization of tests. TG2-IgA showed the highest titer rise with non-adherence to the GFD, independent of the manufacturer.