The aim of this study was to evaluate performance of serum antibodies against deamidated gliadin peptides (a-DGPs) in detecting compliance with gluten-free diet (GFD) in children with celiac disease (CD).
Serum samples were collected the same day of endoscopy in 95 children with CD and 106 controls. We preliminarily calculated the cutoff of a-DGP immunoglobulin A (IgA) and a-DGP IgA+G in our population by receiver operating characteristic (ROC) curves. Of 95 children with CD, 28 were studied during the first year after GFD introduction, with interview and serum collection every 3 months. In addition, serum samples were collected in 106 children with CD on GFD for more than 1 year (range 1–14). In both groups of children with CD on GFD, we compared a-DGP IgA and IgA+G performance in monitoring compliance with GFD with anti-tissue transglutaminase antibodies (anti-tTG) IgA and anti-gliadin antibody (AGA) IgA.
The cutoff resulted in 13.1 arbitrary units (AU) for a-DGP IgA (sensitivity 87.4, 95% confidence interval [CI] 79%–92%, specificity 97.2, 95% CI 92%–99%) and 16.5 for a-DGP IgA+G (sensitivity 94.7, 95% CI 88%–98%, specificity 89.6, 95% CI 84%–95%). In the first year of GFD, at 6 to 8 months prevalence of positive a-DGPs was significantly higher in partially versus strictly compliant children, and at 9 to 12 months only prevalence of positive a-DGP IgA+G remained significantly higher. Moreover, at 9 to 12 months sensitivity to detect transgressions to GFD was 44% for a-DGP IgA and 100% for a-DGP IgA+G (P = 0.03). In the 106 children on GFD for more than 1 year, sensitivity to detect transgressions to GFD was 60% for a-DGP IgA and 76% for a-DGP IgA+G. Anti-tTG IgA and AGA IgA sensitivity was much lower (24% and 4%, respectively). The 4 tests showed comparable high specificity.
Both a-DGPs showed higher sensitivity than anti-tTG IgA and AGA IgA in monitoring compliance with GFD, but a-DGP IgA+G seemed to perform better. a-DGPs did not outperform anti-tTG IgA for CD screening.
*Department of Pediatrics, Università del Piemonte Orientale, Italy
†Microbiology Laboratory, Maggiore della Carità Hospital, Novara, Italy.
Received 21 July, 2010
Accepted 3 February, 2011
Address correspondence and reprint requests to Prof Giuseppina Oderda, Department of Pediatrics, Università del Piemonte Orientale, Via Solaroli 17, 28100 Novara, Italy (e-mail: firstname.lastname@example.org).
The study was partially sponsored by a grant of the Regione Piemonte government, which took no part in designing the study or analyzing the data.
The authors report no conflicts of interest.