Antibodies against deamidated gliadin peptides and tissue transglutaminase for diagnosis of pediatric celiac disease.
The aim of the present study was to evaluate diagnostic performance and actual costs in clinical practice of immumoglobulin (Ig)G/IgA deamidated gliadin peptide antibodies (DGP) as a complement to IgA antibodies against tissue transglutaminase (tTG) for the diagnosis of pediatric celiac disease (CD). All of the consecutive patients younger than 18 years tested for tTG and/or DGP, who underwent duodenal biopsy because of suspected CD in Stockholm and Gothenburg, Sweden, from 2008 to 2010, were included. Medical records were reviewed. Of 537 children who underwent duodenal biopsy, 278 (52%) had CD. A total of 71 (13%) were younger than 2 years and 16 (4%) had IgA deficiency. Sensitivity and specificity for tTG were 94% and 86%, respectively. Corresponding values for DGP were 91% and 26%. Positive predictive values (PPV) were 88% for tTG and 51% for DGP. There were 148 children who were tTG-negative and DGP-positive, of which only 5% (8/148) had villous atrophy. Among children younger than 2 years with normal IgA, PPV was 96% (25/26) for tTG and 48% (24/50) for DGP. In 16 IgA-deficient children, 11 were DGP positive, of which 5 had CD (PPV 45%). Eight of 278 cases of CD would possibly have been missed without DGP. The cost of adding DGP and consequently more biopsies to be able to detect 8 extra cases of CD was [Euro sign]399,520 or [Euro sign]49,940 per case. For diagnosing CD, tTG is superior to DGP, even in children younger than 2 years. Combining tTG and DGP does not provide a better tradeoff between number of missed cases of CD, number of unnecessary duodenal biopsies, and cost than tTG alone.