To DGP-IgG or not? a comparison of TTG-IgA and DGP-IgG

We assessed the diagnostic utility of deamidated gliadin peptide immunoglobulin G (DGP-IgG) in pediatric patients without immunoglobulin A deficiency who underwent tissue transglutaminase immunoglobulin A (TTG-IgA) screening and biopsy.

Patients who had TTG-IgA performed in our laboratory had sample frozen over 1.5 y. If a patient underwent biopsy within 6 months of serology, DGP-IgG was performed on frozen sample. All testing was performed on the BioPlex 2200. Biopsies were assigned a modified Marsh-Oberhuber score. The sensitivity, specificity, and positive and negative predictive values were calculated for TTG-IgA and DGP-IgG for values ≥ 15 u/ml, 15-149 u/ml, and ≥ 150 u/ml using biopsy as gold standard.

A total of 458 patients were included. Sensitivity and specificity for DGP-IgG ≥ 15 u/ml and Marsh ≥ 2 was 76% and 87.5% and TTG-IgA ≥ 15 was notably higher at 93.3% and 92.2%. Sensitivity and specificity of DGP-IgG were 66% and 88.9% at moderate and 29.3% and 98.4% at high increases. The positive predictive value of DGP-IgG for celiac disease in TTG-IgA negative patients was 2.8%.

Our study suggests DGP-IgG does not add significant value in patients screened for celiac disease.