A reliable screening test for coeliac disease: enzyme‐linked immunosorbent assay to detect anti‐gliadin antibodies in serum

Abstract

A simple, rapid, highly reproducible enzyme-linked immunosorbent assay detecting anti-gliadin antibodies in serum to screen for coeliac disease (CD) is described. By combining the results of anti-gliadin IgA and IgG determinations the overall sensitivity of the assay was found to be 100% and the specificity 96% for children and 99% for adults. Significantly elevated antigliadin IgA and IgG antibodies were detected in all 20 children and all 25 adults with untreated CD. False positive results were found in 1/79 histologically normal control and 5/86 disease control children, while for adults false positive rates were 0/74 and 1/34 for the healthy and disease control groups, respectively. Anti-gliadin IgA and IgG was measured in serum samples from 52 coeliac patients (11 children and 41 adults) treated with a gluten-free diet (GFD). Each of the children and 28 of the adults who followed a strict GFD had significantly lower IgA and IgG levels than untreated CD patients. The serum anti-gliadin IgA and IgG levels of the 13 adults not complying with a GFD were similar to those found for untreated CD patients. This assay is recommended as a screening test for CD as well as a tool for follow-up of treated patients.

Differentiation of Coeliac Disease and Other Malabsorption Diseases Using Specific Serum Antigliadin IgG Subclass Profiles and IgA1 Levels

“…1, 2). As had been noted earlier for total gliadin-specific IgG [19], the extent of decline of individual antigliadin IgG subclass lev els was greater in GFDc children than adults. IgG4 levels in virtually all patients had returned to very low levels, and IgG3 levels were lower than in untreated CD for the ma jority of compliant treated patients.…”

“…They attributed this im proved discriminatory potential of the antigliadin IgAl as say, compared with total antigliadin IgA, to the higher specificity and affinity of the particular monoclonal antibody-increasing sensitivity without increasing background activity. This conclusion seems questionable since ELISA methods using polyclonal antibodies can be adjusted to yield negligible background activity [5,19], It seems more likely that the assay used by Elewaut et al [17] to detect to tal gliadin-specific IgA was not sufficiently sensitive, re sulting in false negative findings. It is important to note also that coeliac patients with selective IgA deficiency will fail to be detected if screened for IgAl only.…”

“…The method was characterised by the same parameters as those used for our earlier study [19]. Cut-off val ues (COV), determined as the mean plus 2 standard deviations (SD) of ELISA absorbance values obtained for the histologically normal and healthy control groups were earlier found to yield best distinc tion of coeliac and non-cocliac samples [19], so this was used for sub class COV determination in the current study. Results were consid ered positive and indicative of CD when they exceeded the appropri ate COV.…”

“…Results were consid ered positive and indicative of CD when they exceeded the appropri ate COV. For the IgA-lgG test, results were considered indicative of CD only when both anti-gliadin IgA and IgG were simultaneously elevated above their appropriate COV, provided there was no coex isting immunoglobulin deficiency [19].…”

“…All samples in the study were stored at -20 °C until assayed. Total antigliadin IgA and IgG levels were determined for each serum sample using an ELISA method, as previously described [19]. This assay was adapted to measure antigliadin IgA and IgG sub classes in serum, as decribed below.…”