Diagnostic efficacy of the ELISA test for the detection of deamidated anti-gliadin peptide antibodies in the diagnosis and monitoring of celiac disease

"Per ELISA": Time to adopt anti-transglutaminase/deamidated gliadin peptide diagnostic combination in coeliac disease of adults?

BACKGROUND

Anti-endomysial antibodies (EMA) and anti-tissue transglutaminases (a-tTg) play a pivotal role in coeliac disease (CD) diagnosis. Deamidated anti-gliadin peptides (DGP) were added to the CD diagnostic workup.

AIMS

We aimed to compare the diagnostic accuracies of ELISA-based (a-tTg/DGP) and immunofluorescence-ELISA-based strategies (EMA/a-tTg) for CD diagnosis.

METHODS

From November 2020 to November 2022, we undertook an observational prospective study including consecutive adult patients with suspected CD. All subjects were tested for EMA, a-tTg and DGP IgA. An ROC curve was plotted to establish the best specificity cut-off of a-tTg and DGP levels, which would predict the presence of Marsh≥2 and Marsh=3. The diagnostic accuracies of a-tTg/DG and EMA/a-tTg were compared.

RESULTS

The study included 275 CD patients. Histology showed Marsh=1 in 9.9%, Marsh=2 in 4.5%, and Marsh=3 in 85.6.%. The best cut-off value of a-tTg for predicting Marsh≥2 was 42 U/mL, while the best cut-off for predicting atrophy was 68.4 U/mL. The best cut-off value of DGP for predicting Marsh≥2 was 56 U/mL, while the best cut-off for predicting atrophy was 78 U/mL. A-tTg/EMA showed 97% sensitivity and 100% specificity, whereas a-tTg/DGP showed 94% sensitivity and 100% specificity.

CONCLUSION

A-tTg/DGP is accurate for CD diagnosis and could reduce costs and operator-dependency of EMA. DGP, together with a-tTg, could replace EMA in CD diagnosis.

Dynamics of Serologic Change to Gluten in Celiac Disease Patients

Serologic measures of tissue transglutaminase (tTG) immunoglobulin A (IgA) and deamidated gliadin peptide (DGP) IgA and immunoglobulin G (IgG) are hallmark tests utilized when diagnosing individuals for celiac disease (CeD) and for monitoring adherence to a gluten-free diet (GFD), currently the only available treatment for CeD. We address two issues in this study: (i) the relapse to seropositivity for CeD patients who resume a gluten containing diet and (ii) the correlation between two different tTG-IgA assays near the upper limit of normal (ULN) designated thresholds. Regarding the first issue, often a suspected CeD individual is put back on a gluten diet to return to their serologic levels. However, we show it requires a substantial amount of gluten for serology to return to a positive level. For example, in one study of 22 patients treated with placebo and taking 84 g of gluten over 6 weeks, only two converted from seronegative to seropositive for tTG-IgA. Regarding the second topic, we compare the relationship for different serologic assays, namely tTG-IgA AB (recombinant, ULN = 4 units/mL) vs. tTG-IgA (non-recombinant, ULN = 20 units). There is a strong correlation between both measurements as evidenced by a Pearson coefficient of R = 0.8584; however, we observed that the cross-correlation in terms of sensitivity and specificity improved substantially by using an ULN value of three instead of four for the tTG-IgA AB (recombinant) assay. This result suggests that assay thresholds used for initial diagnosis in patients who have not yet started a GFD may need to be adjusted for monitoring and in the setting of a diagnostic gluten challenge.

Association of Celiac Disease With Pembrolizumab

Immune checkpoint inhibitors (ICIs) in the recent times have transformed the landscape of the management of many solid tumors. Unfortunately, many immune-related adverse effects are associated with ICIs, which lead to a negative outcome in cancer treatment. We present a case of a 63-year-old female with metastatic adenocarcinoma of unknown origin, who developed celiac disease during the course of treatment with pembrolizumab. Association of celiac disease with this form of immunotherapy has never been documented before.

Influence of the 2012 European Guidelines in Diagnosis and Follow-up of Coeliac Children With Selective IgA Deficiency

OBJECTIVES

The aim of the study was to describe diagnostic criteria used in children with coeliac disease (CD) and selective IgA deficiency; to determine if the publication of the 2012 ESPGHAN criteria prompted any changes; to evaluate the evolution of serological markers.

METHODS

Multicenter, retrospective, descriptive study of a cohort of children under 15 years with selective IgA deficiency diagnosed with CD (January 2006 to December 2016). Demographic, clinical, genetic, histological and IgG-based antibodies were collected at diagnosis and follow-up.

RESULTS

Eighty-six children were included, 60 diagnosed after the guide. Two groups were established: G1 (n = 63) and G2 (n = 23) with or without diagnostic biopsy respectively. In G1: 87.3% were symptomatic, 87.3% had human leukocyte antigan (HLA) DQ2/DQ8 typing (all positive), all had IgG serology positive (71.5% ATG, 35% EMA, 19% DPG, 9.5% AGA), and all had villous atrophy (Marsh-Oberhuber 2-3). Follow-up data were available in 58 children, 34 after 2 years on a gluten-free diet. Fifty-two percentage remained ATG IgG-positive despite good dietary adherence and symptom remission. Regarding G2: all were diagnosed post-2012, had typical symptoms, HLA DQ2/DQ8 positive and ATG IgG × 10 ULN. Additionally, EMA IgG was performed in 14 (60%), all positive.

CONCLUSIONS

In our cohort of children with selective IgA deficiency and diagnosed with CD, children without a diagnostic biopsy suggests that IgG serology was considered the equivalent as IgA isotype, even when this is not addressed in the aforementioned guidelines. Great heterogeneity was observed in the IgG serology used at diagnosis. After 2 years of a gluten-free diet, half of children remained with a positive serology.

Coeliac disease in infants: antibodies to deamidated gliadin peptide come first!

Background

The onset of coeliac disease (CD) in the first year of life is uncommon and the diagnosis can be challenging due to the suboptimal sensitivity of tissue transglutaminase antibodies (tTG) at this age and the many other possible causes of malabsorption in infants. Antibodies to deamidated gliadin peptides (anti-DGPs), especially IgG, may appear earlier than IgA anti-tTG in very young children with CD.

Case presentation

We report here on an 8-month-old child who was evaluated for failure to thrive, constipation and developmental delay. The symptoms started following gluten introduction in the diet. Laboratory tests showed high fecal elastase concentration, normal serum IgA levels with positive IgG and IgA anti-DGPs, whereas anti-tTG were not detected. The duodenal biopsy revealed a complete villous atrophy (Marsh-Oberhuber 3C). The culture of biopsy fragments in the presence of gliadin peptides did not stimulate the production of IgA anti-endomysial antibodies. Genetic testing proved the child was positive for HLA-DQ2 (DQA1*05; DQB1*02) and HLA-DQ8 (DQA1*03, DQB1*0302). Having initiated the gluten-free diet, the symptoms disappeared and the infant experienced rapid catch-up growth with normalization of psychomotor development.

Conclusions

This case report highlights the utility of anti-DGPs for screening infants with suspected CD. The pattern with positivity for IgG and IgA anti-DGPs only is rare in IgA-competent children with biopsy-proven CD. It could be explained in infancy as immaturity of the adaptive immune system.

Evidence-Informed Expert Recommendations for the Management of Celiac Disease in Children

Although the need for effective long-term follow-up for patients with celiac disease (CD) has been recognized by many expert groups, published practice guidelines have not provided a clear approach for the optimal management of these patients. In an attempt to provide a thoughtful and practical approach for managing these patients, a group of experts in pediatric CD performed a critical review of the available literature in 6 categories associated with CD to develop a set of best practices by using evidence-based data and expert opinion. The 6 categories included the following: bone health, hematologic issues, endocrine problems, liver disease, nutritional issues, and testing. Evidence was assessed by using standardized criteria for evaluating the quality of the data, grade of evidence, and strength of conclusions. Over 600 publications were reviewed, and 172 were chosen for inclusion. The thorough review of the results demonstrated that the quality of the data available was often insufficient to provide unequivocal best practices. However, using the available data and the clinical experience of the panel, a practical framework for the management of children with CD was created. These recommendations were developed by our expert panel and do not necessarily reflect the policy of the American Academy of Pediatrics. The potential usefulness of these best practices is underscored by the fact that consensus, measured by the outcome of anonymous voting, was reached by the panel for 24 of the 25 questions. We hope that these best practices may be useful to the pediatric gastroenterology and larger general pediatric communities.

Overview of biomarkers for diagnosis and monitoring of celiac disease

Among the adverse reactions caused by wheat, celiac disease (CD) is the longest studied and best-known pathology. The more recently defined non-celiac gluten sensitivity (NCGS) presents with symptoms which are often indistinguishable from CD. Diagnosis of CD is based on serologic, molecular, and bioptic testing. The IgA anti-transglutaminase (tTG) test is considered highly important, as it shows high sensitivity and specificity and its levels correlate to the degree of intestinal damage. Small bowel biopsy can be avoided in symptomatic patients with IgA anti-tTG levels above 10× the manufacturer's cut-off. Recently, tests of anti-deamidated peptides of gliadin (DGP) have replaced classic anti-native gliadin (AGA) tests. DGP assays have a considerably higher diagnostic accuracy than AGA assays, especially in the IgG class, and can replace anti-tTG tests in patients with selective IgA deficiency. The combination of IgG anti-DGP plus IgA anti-tTG assays show greater sensitivity than a single test, with very high specificity. EMA tests have great diagnostic accuracy but are not recommended by all the latest guidelines because they are observer dependent. Biopsy must still be considered the gold standard for CD diagnosis. HLA-DQ genotyping can be used to screen asymptomatic children and in cases of histology/serology disagreement. About half of NCGS patients are DQ2 positive and have IgG AGA. To diagnose NCGS, first CD and wheat allergy must be excluded; then the wheat dependence of symptoms must be verified by a gluten-free diet and subsequent gluten challenge.

Serological testing for celiac disease in adults

BACKGROUND AND AIM

We present a systematic review on the performance of currently available methods for serological diagnosis of celiac disease (CD) and the role of human leukocyte antigen (HLA) typing.

OBJECTIVE

A literature survey was conducted using PubMed, MeSH database, Web of Science as well as manual searches.

RESULTS

Tissue transglutaminase antibodies (tTG) (IgA) (tested in nine studies) show sensitivities and specificities in the range of 0.76-0.968 and 0.909-0.98, and deamidated gliadin peptide (DGP) (IgA and IgG) (tested in eight studies) show sensitivities and specificities in the range of 0.69-0.984 and 0.903-1. Endomysial antibodies (EMA) (tested in five studies) show sensitivities and specificities in the range of 0.61-0.937 and 0.98-1, respectively. Combination assays (tested in three studies) using DGP + tTG and DGP (IgA + IgG) show sensitivities and specificities in the range of 0.87-1 and 0.8-1, respectively. HLA DQ2/DQ8 may be necessary for the development of CD-HLA DQ2 in particular. A possible close correlation may also exist between CD and HLA-G.

CONCLUSION

DGP and tTG for serological testing for CD show equivalent diagnostic performance. More studies with, in particular, DGP alone and in combination with tTG are necessary before a firm recommendation can be made. HLA typing to exclude CD may still be controversial. It still seems premature to diagnose celiac disease in adults based on serology alone.

Serological assessment for celiac disease in IgA deficient adults

PURPOSE

Selective immunoglobulin A deficiency is the most common primary immunodeficiency disorder that is strongly overrepresented among patients with celiac disease (CD). IgG antibodies against tissue transglutaminase (tTG) and deamidated gliadin peptides (DGP) serve as serological markers for CD in IgA deficient individuals, although the diagnostic value remains uncertain. The aim of this study was to investigate the prevalence of these markers in a large cohort of IgA deficient adults with confirmed or suspected CD and relate the findings to gluten free diet.

METHODS

Sera from 488,156 individuals were screened for CD in seven Swedish clinical immunology laboratories between 1998 and 2012. In total, 356 out of 1,414 identified IgA deficient adults agreed to participate in this study and were resampled. Forty-seven IgA deficient blood donors served as controls. Analyses of IgG antibodies against tTG and DGP as well as HLA typing were performed and a questionnaire was used to investigate adherence to gluten free diet. Available biopsy results were collected.

RESULTS

Out of the 356 IgA deficient resampled adults, 67 (18.8%) were positive for IgG anti-tTG and 79 (22.2%) for IgG anti-DGP, 54 had biopsy confirmed CD. Among the 47 IgA deficient blood donors, 4 (9%) were positive for IgG anti-tTG and 8 (17%) for anti-DGP. Four were diagnosed with biopsy verified CD, however, 2 of the patients were negative for all markers. Sixty-eight of 69 individuals with positive IgG anti-tTG were HLA-DQ2/DQ8 positive whereas 7 (18.9%) of the 37 individuals positive for IgG anti-DGP alone were not.

CONCLUSIONS

IgG anti-tTG seems to be a more reliable marker for CD in IgA deficient adults whereas the diagnostic specificity of anti-DGP appears to be lower. High levels of IgG antibodies against tTG and DGP were frequently found in IgA deficient adults despite adhering to gluten free diet.

Diagnostic dilemmas in celiac disease

Celiac disease (CD) is an immune-mediated systemic condition triggered by dietary gluten occurring in genetically susceptible individuals. Our understanding of its numerous and varied clinical presentations has evolved over time, which has contributed to the incidence of CD increasing. In most cases, the diagnosis is readily established and patients promptly improve after commencing a gluten-free diet (GFD). However, in some, the diagnosis is not straightforward and presents a challenge to clinicians. Potential dilemmas include those with positive serology but normal histology, negative serology but abnormal duodenal mucosal histology, failure to respond to a GFD or response to a GFD without evidence of CD. In recent years, development of new assays and modifications to existing diagnostic algorithms for CD has also challenged the traditional role of small-bowel histology as critical in CD diagnosis.

Prevalence and natural history of potential celiac disease in at-family-risk infants prospectively investigated from birth

OBJECTIVE

To evaluate the frequency and the natural history of potential (serology positive/Marsh 0-1 histology) celiac disease (CD) in children with a family risk of CD and factors associated with potential instead of overt (serology positive/Marsh 2-3 histology) CD expression.

STUDY DESIGN

Two-year follow-up study of 96 children (57 females; mean age: 29 ± 12 months) prospectively investigated from birth with: (1) a CD-affected first-degree relative; (2) positivity of serum IgA anti-tissue transglutaminase (tTG) or IgG antigliadin and IgA deficiency; and (3) the results of small intestinal biopsy. Children with potential CD were advised to remain on a gluten containing diet, repeat the celiac antibodies every 6 months, and to have an intestinal biopsy performed in case of persistently high anti-tTG level. Factors discriminating between potential and overt CD were analyzed by decision tree analysis based on the C4.5 algorithm.

RESULTS

Twenty-four children had potential and 72 overt CD. The stronger predictors of potential CD were lack of symptoms, anti-tTG level lower than 11-fold the upper normal limit, age lower than 24 months, and breastfeeding longer than 8 months. Eighteen out of 21 (86%) patients with potential CD continuing a gluten-containing diet became antibody negative, 1/21 (5%) developed overt CD, and 2/21 (9%) had fluctuating antibodies levels after 2 years.

CONCLUSIONS

The prevalence of potential CD and the percentage of short-term loss of CD-related-antibodies are high in infants at-family-risk for CD. In symptomless children with a positive celiac serology, the decision of performing an intestinal biopsy should be preceded by a period of repeated serological testing.

A novel algorithm for the diagnosis of celiac disease and a comprehensive review of celiac disease diagnostics

There is an urgent clinical need for a better laboratory celiac disease diagnosis with both less false positive results and minimal underdetection. The aim of the present study was to evaluate the performance and diagnostic accuracy of different assays in an outpatient population setting for the diagnosis for celiac disease (CD) in order to design an optimal algorithm. We used 15 different ELISA assays to assess 47 blood samples of newly diagnosed children (positive biopsy results) and 52 samples from age- and sex-matched children with negative biopsy results for CD. Scoring criteria were established for grading the assays performance and characteristics. The combined gliadin and tTG assays exhibited the best sensitivity (100%). The addition of other assays to the CeliCheck neo-epitopes assay improved specificity so that the final algorithm had 100% sensitivity, 96.2% specificity, and 98.1% accuracy. The clinical demand for both maximal sensitivity and maximal specificity cannot be achieved with a single test. Using a combination of a sensitive assay together with specific assays improved celiac disease detection rates, with an acceptable number of false positive results. This model, however, needs to be confirmed prospectively in both children and adults.

The old and new tests for celiac disease: which is the best test combination to diagnose celiac disease in pediatric patients?

BACKGROUND

In the diagnosis of celiac disease (CD), serum assays for anti-endomysium (EMA) and anti-transglutaminase (anti-tTG) antibodies have excellent diagnostic accuracy. However, these assays are less sensitive in young pediatric patients. Recently, a new ELISA test using deamidated gliadin peptides (DGP) as antigen has proved to be very sensitive and specific even in pediatric patients. In addition, anti-actin IgA antibodies (AAA) is another test that can be used in CD patients because antibody concentrations correlate with the degree of villous atrophy. This study evaluated the clinical accuracy of anti-tTG, EMA, AGA, anti-DGP and AAA and the effectiveness of these in different combinations for diagnosing CD in a large cohort of pediatric patients.

METHODS

Sera of 150 children under 6 years of age were tested: 95 patients had a diagnosis of CD, while 55 patients who did not suffer from CD were used as controls. Anti-DGP IgA/IgG and AAA were assayed with ELISA kits, while anti-tTG IgA/IgG and AGA IgG/IgA were assayed using a quantitative fluoroimmunoassay. The EMA test was conducted by indirect immunofluorescence.

RESULTS

Seventy-six of 95 (80%) CD patients were positive for DGP IgA and/or tTG IgA. Eighty of 95 (84.2%) patients were positive for DGP IgG and/or tTG IgA. None of the controls were positive for these antibodies. Eighty-four of 95 (88.4%) patients and 8/55 (14.5%) controls were positive for AAA and/or anti-tTG IgA.

CONCLUSIONS

In very young children, association of anti-tTG IgA with anti-DGP IgG is the best test combination for diagnosing CD, yielding a cumulative sensitivity of 84.2% and a specificity of 100%.

Immunoglobulin G antibodies against deamidated-gliadin-peptides outperform anti-endomysium and tissue transglutaminase antibodies in children <2 years age

To investigate the usefulness of deamidated-gliadin-peptides-antibodies in the diagnosis of celiac disease, serology was tested in 212 children suspected with celiac disease who had undergone a small-intestinal-biopsy. For deamidated-gliadin-peptides-antibodies, two kits were tested. Positive and negative predictive values for IgA deamidated-gliadin-peptides-antibodies using the Bindazyme-kit were 89% and 74%, while the Quanta-Lite-kit had values of 89% and 85%, respectively. For the IgG subtype using the Bindazyme-kit, these values were 85% and 89%, while they were 85% and 91% for the Quanta-Lite-kit. The positive predictive values for endomysium and tissue-transglutaminase antibodies were disappointing (77% and 87%), although the negative predictive values were better (97% and 96%). When the analysis was restricted to the 41 children aged <2 years, no misclassifications occurred with IgG deamidated-gliadin-peptides-antibodies giving 100% accuracy in both kits. The positive predictive value reached 100% for tissue-transglutaminase antibodies and both kits for IgA deamidated-gliadin-peptides-antibodies, while the negative predictive value was 94% in these assays. Positive and negative predictive values for endomysium antibodies were 96% and 93%, respectively. In conclusion, although deamidated-gliadin-peptides-antibodies do not outperform anti-endomysium antibodies in the total study population, the IgG subtype seems to be the best test in children aged <2 years, reaching 100% accuracy.

Use of deamidated gliadin peptide antibodies to monitor diet compliance in childhood celiac disease

OBJECTIVE

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).

PATIENTS AND METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

[Serological diagnosis of celiac disease]

Screening studies using high-sensitivity and specificity markers indicate a prevalence of celiac disease of up to 1% in European and North-American populations. Celiac disease is a frequent condition that has become an important public health issue. Yet the majority of cases remain undiagnosed due to the polymorphism of its clinical manifestations. The new insight in the pathogenesis of celiac disease has lead to the development of new diagnostic tools. Early screening of symptomatic patients and pre-identified at-risk groups significantly improves the quality of life while reducing morbidity and mortality. However, prophylactic benefits of early diagnosis by assessing the general population have not been shown in any study. French and Northern American scientific societies have introduced serological testing in their newly revised strategies to diagnose celiac disease. Older markers judged insufficiently accurate like anti-gliadin and anti-reticulin antibodies have recently been withdrawn from the list of reimbursed medical expenses in France. Anti-endomysium and tissue transglutaminase IgA antibodies have proven to be at this day the most sensitive and specific markers for the diagnosis and follow-up of patients on gluten-free diet, at the exception of IgA-deficient patients. Assays testing for IgG antibodies are recommended upon IgA-deficiency. Although very accurate, a better standardisation of current assays may enable serological testing to replace in a near future histological confirmation brought by small bowel biopsies which remains today the gold standard test to diagnose celiac disease. Indeed, serological testing represents and attractive alternative as it is less invasive, less expansive, laboursaving and more objective in interpretation.

Antibodies against deamidated gliadin peptides identify adult coeliac disease patients negative for antibodies against endomysium and tissue transglutaminase

BACKGROUND

This study was done to evaluate the diagnostic utility of antibodies against deamidated gliadin peptides compared to traditional markers for coeliac disease.

AIM

To evaluate diagnostic utility of antibodies against deamidated gliadin peptide (DGP).

METHODS

Sera from 176 adults, referred for endoscopy without previous analysis of antibodies against tissue transglutaminase (tTG) or endomysium (EmA), were retrospectively analysed by ELISAs detecting IgA/IgG antibodies against DGP or a mixture of DGP and tTG, and compared with IgA-tTG and EmA. Seventy-nine individuals were diagnosed with coeliac disease.

RESULTS

Receiver operating characteristic analyses verified the manufacturers' cut-off limits except for IgA/IgG-DGP/tTG. In sera without IgA deficiency, the sensitivity was higher for IgA/IgG-DGP (0.85-0.87) compared with IgA-tTg (0.76) and EmA (0.61). All tests showed high specificity (0.95-1.00). Eighteen coeliac disease-sera were negative regarding IgA-tTG, nine of which were positive for IgA/IgG-DGP. Sera from coeliac disease-patients >70 years were more often negative for IgA-tTG (50%) and IgA/IgG-DGP (36%) than younger patients (15% and 8% respectively) (P < 0.01). Three of the four IgA-deficient patients were positive in the IgA/IgG-DGP assay.

CONCLUSIONS

In this study of patients unselected regarding IgA-tTg/EmA, thus unbiased in this respect, IgA/IgG-DGP identified adult coeliac disease patients negative for antibodies against endomysium and tissue transglutaminase. Serology is often negative in elderly patients with coeliac disease; a small bowel biopsy should therefore be performed generously before coeliac disease is excluded.

Positive deamidated gliadin peptide antibodies and negative tissue transglutaminase IgA antibodies in a pediatric population: to biopsy or not to biopsy

Reports from our clinical laboratory database show that 75% of children <2 years old tested for celiac serology who were found positive for deamidated gliadin peptide (DGP) antibodies had negative results for tissue transglutaminase IgA. DGP levels were shown to decline and disappear without a gluten-free diet. This observation questions DGP's specificity for diagnosis of celiac disease.

IgG Antibodies against Deamidated Gliadin Peptides for Diagnosis of Celiac Disease in Patients with IgA Deficiency

Background: Assays for IgG antibodies against deamidated gliadin (IgG-anti-dGli) are comparable in performance with tests detecting IgA antibodies against tissue transglutaminase (IgA-anti-tTG) in diagnosing celiac disease (CD). IgA-anti-tTG are absent in IgA deficiency, a condition often associated with CD. In IgA deficiency, IgG-anti-tTG, which have a lower overall diagnostic accuracy, are routinely measured. We examined whether IgG-anti-dGli would be useful for diagnosing CD in patients with IgA deficiency.

Methods: We studied 34 IgA-deficient CD patients, 185 IgA-competent newly diagnosed children with CD, 316 children without CD, 400 adult blood donors, and 6 control IgA-deficient individuals without CD. Anti-dGli and anti-tTG were measured by ELISA, and endomysium antibodies (EmA) were measured by immunofluorescence on monkey esophagus (IgA as well as IgG class for all antibodies). We calculated diagnostic sensitivity (percentage of patients above cutoff with 95% CIs) according to age-specific cutoffs for 95% diagnostic specificity and according to cutoffs proposed by the manufacturer of the assays.

Results: No IgA-deficient CD patients were positive for any IgA-based antibody assay. Diagnostic sensitivity of IgG-anti-tTG was 91.2% (95% CI 76.3%–97.7%) according to age-specific cutoffs and 82.4% (66.1%–92.0%) according to manufacturer cutoffs. The diagnostic sensitivity of IgG-EmA was 75.8% (58.8%–87.4%) and the sensitivity of IgG-anti-dGli was 88.2% (72.8%–95.9%) according to both cutoffs.

Conclusions: IgG-anti-dGli and IgG-anti-tTG have comparable diagnostic sensitivities for IgA-deficient celiac patients. IgG-anti-dGli may be useful for diagnosing CD in IgA-deficient patients.

Diagnostic performance of IgG anti-deamidated gliadin peptide antibody assays is comparable to IgA anti-tTG in celiac disease

BACKGROUND

Detection of IgG antibodies against deamidated gliadin peptides (DGP) is more sensitive and more specific for celiac disease than detection of IgG antibodies against native gliadin. Our aim was to evaluate the technical performance and diagnostic accuracy of four commercial IgG anti-DGP assays.

METHODS

Commercial IgG anti-DGP assays from Euroimmun, Inova, Phadia and The Binding Site were evaluated and their diagnostic accuracy (sensitivity and specificity) compared to other serologic assays for celiac disease (3IgA and 2IgG anti-tTG assays, 1IgA and 1IgG anti-gliadin assay, 1IgA anti-DGP assay). The study population consisted of 86 consecutive CD patients and 741 disease controls.

RESULTS

The technical performance (linearity, interference and imprecision) of the IgG anti-DGP assays was acceptable. The sensitivity of the IgG anti-DGP assays varied between 76.7% and 86.0% at the cut-off recommended by the manufacturer and between 74.4% and 86.0% at the cut-off that corresponded to a specificity of 98%. The specificity varied between 97.3% and 99.3%. The diagnostic accuracy of the IgG anti-DGP assays was comparable to the diagnostic accuracy of the IgA anti-tTG assays. The sensitivity of the IgG anti-DGP assays was significantly better than sensitivity of the IgG anti-tTG assays (p<0.05) and the specificity was significantly better than the IgA and IgG anti-gliadin assays (p<0.05).

CONCLUSIONS

The overall performance of the four IgG anti-DGP assays was acceptable and the diagnostic accuracy comparable to the three IgA anti-tTG assays.