Anti-Deamidated Gliadin Peptides (DGP) IgA ELISA Assay Kit
The Anti-Deamidated Gliadin Peptides (DGP) IgA ELISA Assay Kit is For Research Use Only
Size: 1×96 wells
Sensitivity: 0.74 AU/mL
Dynamic Range: 15 – 240 AU/mL
Incubation Time: 1 hour 15 minutes
Sample Type: Serum, Plasma
Sample Size: 10 µL
Controls Included
Assay Background
Celiac disease (CD) is defined as a chronic small-intestinal, immune-mediated enteropathy precipitated by exposure to dietary gluten (found in cereals such as wheat, barley and rye) in genetically predisposed individuals. It is a common autoimmune disorder, affecting ~1% of the population in many parts of the world. Genetic predisposition to CD is linked principally to several HLA system genes; in particular to genotypes DQ2 and DQ8, which are present in 95-98% of celiac patients and occur in 20-30% of the general. This, non IgE mediated food allergy leads to massive malabsorption disturbances and is characterized by a complete atrophy of the villi and a hyperplasia of the crypts of the upper intestine.
Serological testing for CD has evolved over time; initially these tests involved the detection of anti-Gliadin antibodies (AGA), which were subsequently found to be of low diagnostic value due to lack of sensitivity and specificity. As a result, serological investigations have advanced to involve the detection of antibodies targeted against the auto-antigen (e.g. Tissue Transglutaminase (tTG) IgA / IgG) which remains a key assay for the determination of CD.
It has been demonstrated that celiac subjects synthesize specific antibodies against the agent Gliadin, known as Deamidated Gliadin Peptides (DGP). Anti-DGP antibodies are highly specific markers for identifying gluten-intolerant subjects, differently from the anti-gliadin antibodies, which are also found in healthy subjects or in subjects affected by other enteric disorders and are therefore less specific. The latest generation of assays therefore involve the detection of these anti- DGP antibodies. These assays have been found to perform comparatively well against anti-TG tests and assays detecting anti-DGP IgG have been found to be highly accurate in patients with IgA deficiency.
In pediatric populations there is some indication that anti-DGP assays may provide further uses as these assays have a very high level of diagnostic accuracy in both high and low risk populations. Several studies investigating the assessment of DGP antibody levels in pediatric populations (children under the age of 2 years) have demonstrated 100% diagnostic accuracy of this marker even in cases where normal levels of TG have been determined.
There is an observed inverse association between anti-DGP IgA and IgG, and age at diagnosis, with children aged 7 years and under showing significantly higher values than older patients. Furthermore, it has been found that anti-DGP antibodies precede the appearance of TG antibodies in some children with genetic risk for CD. This gives rise to the possibility of using anti-DGP IgA / IgG assays as an earlier indicator for CD in certain infant populations. A further study in infants found that levels of DGP antibodies correlated with the severity of intestinal damage. Use of the test for anti-DGP IgA and IgG antibodies is also recommended in all subjects, regardless of age, showing symptoms suggestive of CD and in whom the t-TG or EMA autoantibodies are absent or present only at low titers.
Celiac patients on gluten-free diets show a progressive reduction of anti-t-TG and anti-gliadin antibodies. The IgG antibody titer decreases more slowly than the IgA antibody level.
Assay Principle
The Anti-Deamidated Gliadin Peptide (DGP) IgA ELISA Assay Kit is based on the binding of present antibodies in calibrators, controls or prediluted patient samples on the synthetic deamidated Gliadin peptides (DGP) coated on the inner surface of the wells. After a 30 minutes incubation the microplate is washed with wash buffer for removing non-reactive serum components. An anti-human-IgA horseradish peroxidase conjugate solution recognizes IgA class antibodies bound to the immobilized antigens. After a 30 minutes incubation any excess enzyme conjugate, which is not specifically bound is washed away with wash buffer. A chromogenic substrate solution containing TMB is dispensed into the wells. After 15 minutes of incubation the color development is stopped by adding the stop solution. The solutions color changes into yellow. The amount of color is directly proportional to the concentration of IgA antibodies present in the original sample.
