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

Multicenter study to compare the diagnostic performance of CLIA vs. FEIA transglutaminase IgA assays for the diagnosis of celiac disease

OBJECTIVES

Celiac disease (CD) is an immune-mediated enteropathy driven by gluten intake. Presence of tTG-IgA antibodies is important for the diagnosis. However, different tTG-IgA assays are used and test performance may vary. Therefore, a retrospective multicenter study was performed to compare the diagnostic performance of three assays.

METHODS

The fluorescence enzyme-linked immunoassay (FEIA) EliA Celikey IgA (Phadia), the chemiluminescence immunoassays (CLIA) h-tTG IgA QUANTA Flash® (Inova Diagnostics) and the anti-tTG ChLIA IgA (Euroimmun) were compared. Diagnostic samples from CD cases (95 adults; 65 children) and controls (479 adults; 253 children) were included. Samples were blinded and reanalyzed on all platforms.

RESULTS

A high quantitative correlation between platforms was found (p<0.0001). Both CLIA were more sensitive (adults 100%; children 100%) compared to the FEIA (adults 88.4%; children 96.6%). Specificity of all assays was high (≥97.6%) with the FEIA having the highest specificity. A cut-off based on receiver operator characteristic analysis (6.5 U/mL) improved the sensitivity of the FEIA (adults 95.8%; children 100%) without affecting specificity. Cut-off values for the CLIA assays did not need further optimization. With the FEIA, 71% of pediatric cases had a tTG-IgA level ≥10× upper limit of normal compared to 91 and 92% with QUANTA Flash and ChLIA, respectively.

CONCLUSIONS

All platforms have high diagnostic accuracy. The CLIA assays are more sensitive compared to the FEIA assay. A lower cut-off for the FEIA improves diagnostic performance, particularly in adult cases that, as demonstrated in this study, present with lower tTG-IgA levels compared to pediatric cases.

Guidelines of the Italian societies of gastroenterology on the diagnosis and management of coeliac disease and dermatitis herpetiformis

INTRODUCTION

Coeliac disease and dermatitis herpetiformis are immune-mediated diseases triggered by the consumption of gluten in genetically predisposed individuals. These guidelines were developed to provide general practitioners, paediatricians, gastroenterologists, and other clinicians with an overview on the diagnosis, management and follow-up of coeliac patients and those with dermatitis herpetiformis.

METHODS

Guidelines were developed by the Italian Societies of Gastroenterology. Following a systematic literature review, the Grading of Recommendations Assessment, Development and Evaluation methodology was used to assess the certainty of the evidence. Statements and recommendations were developed by working groups consisting of gastroenterologists and a paediatrician with expertise in this field.

RESULTS

These guidelines provide a practical guidance for the diagnosis, management and follow-up of coeliac patients and dermatitis herpetiformis in children and adults, both in primary care and in specialist settings. We developed four sections on diagnosis, gluten-free diet, follow-up and risk of complications in adults, one section focused on diagnosis and follow-up in children and one on the diagnosis and management of dermatitis herpetiformis.

CONCLUSIONS

These guidelines may support clinicians to improve the diagnosis and management of patients with coeliac disease.

Population-based screening for celiac disease reveals that the majority of patients are undiagnosed and improve on a gluten-free diet

The impact of a gluten-free diet (GFD) on screen-detected celiac disease (CD) is currently ambiguous. We aimed to identify the population-based prevalence of undiagnosed adult CD and examine the impact of a GFD on screen-detected CD. In total, 12,981 adults participated in a population-based health study in Tromsø, Norway. Participants with increased levels of anti-tissue transglutaminase-2 IgA or anti-deamidated gliadin peptide IgG were invited to undergo gastroduodenoscopy with both histological and immunohistochemical examination of small-bowel biopsies. The prevalence of previously diagnosed CD was 0.37%. Additionally, the prevalence of previously undiagnosed CD was 1.10%. Thus, 1.47% of the population had CD, of whom 75% were previously undiagnosed. A GFD resulted in significant improvements in overall gastrointestinal symptoms, diarrhea, and health-related quality of life, with reduced abdominal discomfort (76%) and improved levels of energy (58%). The large majority of patients with adult CD were undiagnosed and benefited from a GFD with reduced gastrointestinal symptoms and improved health-related quality of life. In clinical practice, there should be a low threshold for CD testing even in the absence of abdominal complaints because most adult patients appear to consider their symptoms a part of their normal state and therefore remain untested and undiagnosed.Trial registration: Clinical Trials. Gov Identifier: NCT01695681.

Diagnostic Value of Immunoglobulin G Anti-Deamidated Gliadin Peptide Antibody for Diagnosis of Pediatric Celiac Disease: A Study from Shiraz, Iran

PURPOSE

Screening serologic tests are important tools for the diagnosis of celiac disease (CD). Immunoglobulin (Ig)G anti-deamidated gliadin peptide (anti-DGP) is a relatively new autoantibody thought to have good diagnostic accuracy, comparable to that of anti-tissue transglutaminase (anti-tTG) antibody.

METHODS

Pediatric patients (n=86) with a clinical suspicion of CD were included. Duodenal biopsy, anti-tTG, and IgG anti-DGP antibody tests were performed. The patients were divided into CD and control groups based on the pathological evaluation of duodenal biopsies. The diagnostic accuracy of serological tests was determined.

RESULTS

IgA anti-tTG and IgG anti-DGP antibodies were positive in 86.3% and 95.4% of patients, respectively. The sensitivity, specificity, and diagnostic accuracy of the IgA anti-tTG test were 86.3%, 50.0%, and 68.6%, respectively, and those of the IgG anti-DGP test were 95.4%, 85.7%, and 90.7%, respectively. The area under the receiver operating characteristic (ROC) curve was 0.84 (95% confidence interval [CI], 0.74-0.91) for IgA anti-tTG test and 0.93 (95% CI, 0.86-0.97) for IgG anti-DGP test. The comparison of IgA anti-tTG and IgG anti-DGP ROC curves showed a higher sensitivity and specificity of the IgG anti-DGP test.

CONCLUSION

IgG anti-DGP is a reliable serological test for CD diagnosis in children. High tTG and DGP titers in the serum are suggestive of severe duodenal atrophy. The combined use of IgA anti-tTG and IgG anti-DGP tests for the initial screening of CD can improve diagnostic sensitivity.

Extra-Intestinal Manifestations of Celiac Disease: What Should We Know in 2022?

Celiac disease (CD) is a chronic, small-intestinal, immune-mediated enteropathy due to gluten exposition in genetically predisposed individuals. It occurs in about 1% of the population and often remains an underdiagnosed condition. This could be due to the fact that the adult population often lacks the classical signs and symptoms of CD, manifesting only atypical symptoms. In this review we analyzed the main extra-intestinal manifestations of CD which include cutaneous and endocrinological disorders, abnormal liver function tests, and neuropsychiatric features. When CD is not diagnosed and therefore is not treated with a gluten-free diet (GFD), it can predispose to severe complications, not only gastrointestinal. Thus, it is important for clinicians to quickly recognize the atypical manifestations of CD, considering that an early diagnosis can significantly impact on a patient's prognosis.

Deamidated Gliadin Antibodies: Do They Add to Tissue Transglutaminase-IgA Assay in Screening for Celiac Disease?

OBJECTIVES

Use of deamidated gliadin peptide (DGP) test kits as adjunctive to tissue-transglutaminase-IgA (TTG-IgA) for the diagnosis of celiac disease (CD) has been a controversial issue. The objectives of our study were to evaluate the diagnostic performance of DGP antibodies compared with TTG-IgA and to evaluate the correlation between DGP-antibody titers and degree of enteropathy.

METHODS

We included children who underwent endoscopy and biopsies because of positivity of any of the serology tests in the "celiac profile" (TTG-IgA, DGP-IgA, and DGP-IgG) from 2012 to 2019. We divided children into clinically suspected cases of CD (group 1) and asymptomatic cases screened as they were from a high-risk group (group 2).

RESULTS

Group 1 constituted 52 children and group 2 included 81 children (76 type-1 diabetes [T1D]). The sensitivity and positive-predictive value (PPV) of DGP-IgG in group 1 (90%, 98%) and group 2 (91%, 85.5%) were comparable with TTG-IgA (98%, 92% in group 1; 100%, 80% in group 2). By adding DGP-IgG to TTG-IgA, the performance of TTG-IgA has improved marginally in group 1 (sensitivity 100%, PPV 92.3%). All cases with DGP-IgG titer 2 times ULN in group 1, and >4 times ULN in group 2 had villous atrophy. All T1D patients with TTG IgA >10 times ULN had villous atrophy.

CONCLUSIONS

DGP-IgG assay did not add to the performance of TTG-IgA. DGP-IgG titer correlated with enteropathy. The diagnosis of CD can be made in asymptomatic T1D child with TTG-IgA titer >10 times ULN and positive endomyseal antibodies.

Estimating the Impact of Verification Bias on Celiac Disease Testing

GOAL

The goal of this study was to estimate the impact of verification bias on the diagnostic accuracy of immunoglobulin A tissue transglutaminase (IgA tTG) in detecting celiac disease as reported by an authoritative meta-analysis, the 2016 Comparative Effectiveness Review (CER).

BACKGROUND

Verification bias is introduced to diagnostic accuracy studies when screening test results impact the decision to verify disease status.

MATERIALS AND METHODS

We adjusted the sensitivity and specificity of IgA tTG reported by the 2016 CER with the proportion of IgA tTG positive and negative individuals who are referred for confirmatory small bowel biopsy. We performed a systematic review from January 1, 2007, to July 19, 2017, to determine these referral rates.

RESULTS

The systematic review identified 793 articles of which 9 met inclusion criteria (n=36,477). Overall, 3.6% [95% confidence interval (CI): 1.1%-10.9%] of IgA tTG negative and 79.2.2% (95% CI: 65.0%-88.7%) of IgA tTG positive individuals were referred for biopsy. Adjusting for these referral rates the 2016 CER reported sensitivity of IgA tTG dropped from 92.6% (95% CI: 90.2%-94.5%) to 57.1% (95% CI: 35.4%-76.4%) and the specificity increased from 97.6% (95% CI: 96.3%-98.5%) to 99.6% (95% CI: 98.4%-99.9%).

CONCLUSIONS

The CER may have largely overestimated the sensitivity of IgA tTG due to a failure to account for verification bias. These findings suggest caution in the interpretation of a negative IgA tTG to rule out celiac disease in clinical practice. More broadly, they highlight the impact of verification bias on diagnostic accuracy estimates and suggest that studies at risk for this bias be excluded from systematic reviews.

Anti-transglutaminase IgA antibody measurement in coeliac disease: Method comparison IDS-iSYS vs. Thermo Fisher Phadia

In coeliac disease, the diagnostic work-up is based on a combination of clinical, histopathological and serological evaluation. Among the serological tests, the presence of tissue transglutaminase (tTG) IgA antibodies is the cornerstone owed to a high sensitivity and specificity. Recently, Immunodiagnostic Systems Ltd (IDS) introduced the fully automated chemiluminescent autoimmune assays for use on the IDS-iSYS Multi-Discipline Automated System. In this study, we aimed to compare the performance of the IDS-iSYS assay to the Thermo Fisher Phadia assay and to establish the upper reference limit of tTG IgA in a healthy population from Denmark based on the IDS-iSYS assay. We discovered a total imprecision of CV = 12.2% (2.87 AU/mL) and CV = 10.6% (47.55 AU/mL). Moreover, we compared the performance of IDS-iSYS assay to Thermo Fisher Phadia assay in 236 samples from unselected patients submit for tTG IgA testing and found a concordance of 97% (p < .0001). Furthermore, in 150 healthy blood donors, we established the upper reference limit of 3.26 AU/mL (95% CI: 3.10 - 3.90) was identified. Our study validates the performance of the IDS-iSYS tTG IgA assay and demonstrates results in concordance with the established Thermo Fisher Phadia. Furthermore, it provides estimates for the upper reference interval limit of the tTG-IgA.

Generation of High Affinity Anti-Peptide Polyclonal Antibodies Recognizing Goat αs1-Casein

The chemical, technological and allergy properties of goat's milk are significantly affected by the level of αs1-casein. Detection and quantification of αs1-casein requires high-specificity methods to overcome high-sequence similarity between this protein and others in the casein family. Unavailability of antibodies with high affinity and specificity towards goat αs1-casein hinders the development of immuno-based analytical methods such as enzyme-linked immunosorbent assay (ELISA) and biosensors. Here, we report the generation of polyclonal antibodies (or immunoglobulins, IgGs) raised towards goat αs1-casein N- (Nter) and C-terminal (Cter) peptide sequences. The Nter and Cter peptides of goat αs1-casein were immunized in rabbits for the generation of antisera, which were purified using protein G affinity chromatography. The binding affinity of the antisera and purified IgGs were tested and compared using indirect ELISA, where peptide-BSA conjugates and goat αs1-casein were used as the coating antigens. The Nter antiserum displayed higher titer than Cter antiserum, at 1/64,000 and 1/32,000 dilutions, respectively. The purification step further yielded 0.5 mg/mL of purified IgGs from 3 mL of antisera. The purified Nter IgG showed a significantly (p < 0.05) higher binding affinity towards peptide-BSA and goat αs1-casein, with lower Kd value at 5.063 × 10-3 μM compared to 9.046 × 10-3 μM for the Cter IgG. A cross-reactivity test showed that there was no binding in neither Nter nor Cter IgGs towards protein extracts from the milk of cow, buffalo, horse and camel. High-quality antibodies generated will allow further development of immuno-based analytical methods and future in vitro studies to be conducted on goat αs1-casein.

Optimization of serologic diagnosis of celiac disease in the pediatric setting

BACKGROUND

The clinical presentation of celiac disease (CD) varies between children. The objective of this study was to document the pre-test probability for CD based on symptoms and routine laboratory test and to evaluate the performance of two IgA anti-tissue transglutaminase (tTG) assays. We critically reviewed the concept of using multiples of the manufacturer's upper limit of normal (ULN), as proposed in the ESPGHAN guidelines (if IgA tTG is >10 times ULN, no biopsy is needed).

METHODS

The retrospective study included 91 children with newly diagnosed CD and 605 controls (<16 years). All underwent upper endoscopy with small bowel biopsies. Four laboratory parameters and 16 symptoms were registered. All patients were tested for IgA anti-tTG antibodies with assays from Inova Diagnostics and Thermo Fisher Scientific.

RESULTS

Some combinations of clinical symptoms and laboratory parameters had a high pre-test probability for CD, such as (combinations of) anorexia, failure to thrive, low ferritin level and elevated AST. The diagnostic performance of both IgA anti-tTG assays was excellent and comparable (no difference in ROC curve area under the curve). At a threshold that corresponds to a specificity of 100% (5 times ULN for Inova Diagnostics and 2 times ULN for Thermo Fisher), the sensitivity was 82% for both assays. At the 10 times ULN threshold, the sensitivity differed between the assays (77% vs. 57%), indicating that such threshold does not completely align interpretation across companies.

CONCLUSIONS

Our study showed that some combinations of symptoms and aberrant laboratory parameters had a high pre-test probability. The use of the ESPGHAN non-biopsy approach could reduce small bowel biopsies, but thresholds for IgA-tTG levels are not aligned across assays and should be based on predefined likelihood ratios or specificity.

In Screening for Celiac Disease, Deamidated Gliadin Rarely Predicts Disease When Tissue Transglutaminase Is Normal

OBJECTIVE

While tissue transglutaminase (tTG) antibodies are the most established serological test for celiac disease, newer deamidated gliadin peptide (DGP) screening tests are increasingly being completed. No pediatric study has systematically assessed the incidence of celiac disease in patients with an isolated positive DGP result. We sought to determine the positive predictive value of DGP serology for biopsy-confirmed celiac disease in pediatric patients with elevated DGP and normal tTG, to help guide clinicians' decision making when screening for this common condition and avoid unnecessary invasive follow-up diagnostic testing.

METHODS

A multicenter retrospective review of children, from birth to age 18, with isolated DGP immunoglobulin G (IgG) positive serology referred to 3 Canadian centers was completed. The positive predictive value of an isolated elevated DGP result was calculated.

RESULTS

Forty patients with DGP positive, tTG negative serology underwent endoscopy with duodenal biopsy. Of these, only 1 patient had biopsy-confirmed celiac disease. This patient was IgA deficient. This yields a positive predictive value of 2.5% (95% confidence interval 0.1%-14.7%) for isolated DGP IgG positive serology.

CONCLUSIONS

In isolation, DGP positive serology has a poor positive predictive value for celiac disease in children, especially in IgA sufficient individuals. Our findings suggest that DGP IgG testing should not be completed as part of the initial screening for celiac disease in the pediatric population as it does not effectively differentiate between individuals with and without the disease. Further research is needed to clarify to role of DGP IgG in children under the age of 2 and those with IgA deficiency.

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.

The prevalence of celiac disease in patients with irritable bowel syndrome and its subtypes

Introduction

Irritable bowel syndrome (IBS) and celiac disease (CD) share some gastrointestinal symptoms. Celiac disease should be considered in a differential diagnosis of IBS.

Aim

To estimate the prevalence of predispositions to CD in patients with IBS and its subtypes.

Material and methods

The study included 48 patients (40 women, 8 men; average age: 41.1 ±14.6 years) with IBS, and a control group: 20 healthy volunteers. All participants completed a questionnaire on their current gastrointestinal symptoms and had a blood sample taken to determine the HLA-DQ2/DQ8 antigens and serum concentration of anti-tTG IgA and anti-DGP IgA and IgG.

Results

The presence of HLA-DQ2 or DQ8 was found in 50% of patients (n = 24) with IBS. In the control group the presence of HLA-DQ2 was found in 4 (20%) patients and nobody had HLA-DQ8. Increased levels of anti-tTG IgA were found in 5 (10.42%) patients with IBS, anti-DGP in 4 (8.33%), and anti-DGP IgG in 3 (6.25%). In the control group positive test result for anti-tTG was found in 2 (10%) patients; nobody had elevated anti-DGP IgA or IgG. A concomitant positive result of genetic testing and any elevated serum antibodies specific to CD was found in 12.5% of IBS patients (n = 6) and in none of the control group.

Conclusions

Patients with IBS, regardless of the subtype, significantly more often than healthy controls have the predisposing genetic factors (HLA-DQ2/DQ8) underlying the development of CD.

Assessment of a Test for the Screening and Diagnosis of Celiac Disease

BACKGROUND

Celiac disease (CD) is an immune-mediated intolerance to dietary gluten, affecting genetically predisposed individuals. ELISA-based serological tests help to decide if further duodenal biopsy is necessary, for this the diagnostic kits have to be accurate, specific, and sensible. In this study, we investigate the performance of an ELISA that uses the purified cross-linked complex of tissue transglutaminase and gliadin, referred as the "neoepitope" (AESKULISA® tTG New Generation), as antigen.

METHODS

We evaluated 41 newly diagnosed celiac patients, 18 celiac patients on gluten-free diet, and 169 controls, comprising healthy subjects, patients affected by other autoimmune diseases, and patients affected by several non-autoimmune diseases.

RESULTS AND CONCLUSION

The assay has an excellent performance. Due to its high level of diagnostic accuracy, this assay constitutes a new approach for the screening of celiac patients not only for the diagnosis of CD, but also for monitoring patients on gluten-free diet and their compliance. Moreover, cases of neoepitope-positive subjects who were tested negative with "classical" serological markers could have a predictive value for this pathology. This aspect will require further studies of elaboration.

Immunoglobulin A deficiency in celiac disease in the United States

BACKGROUND AND AIMS

Multiple European studies report increased prevalence of selective immunoglobulin A deficiency (SIgAD) and partial immunoglobulin A deficiency (PIgAD) in patients with celiac disease (CD). However; prospective data representing North American adults are lacking. While SIgAD precludes the use of IgA-tissue-transglutaminase antibody (IgA-tTG), the effect of PIgAD on IgA-tTG sensitivity is not well documented. We aim to determine the prevalence and impact of IgA deficiency on CD presentation and diagnosis in North American adult patients.

METHODS

We reviewed 1000 consecutive patients undergoing IgA-tTG testing and 243 healthy controls. Eligible sera were tested for IgA-tTG, serum immunoglobulins, and IgA/IgG-deamidated gliadin peptide (IgA/IgG-DGP).

RESULTS

Prevalence of SIgAD was marginally higher in patients with CD (1.9%) compared with healthy controls (0.4%, P = 0.24) and patients without CD (0.7%, P = 0.173). Prevalence of PIGAD was similar in patients with CD (4.8%) compared with healthy controls (5.9%, P = 0.57) and patients without CD (7.2%, P = 0.22). One (16.7%) of 6 patients with CD with SIgAD and all 15 (100%) with PIGAD tested IgA-tTG positive prior to gluten-free diet initiation. Patients with CD with SIGAD showed lower frequency of gastrointestinal symptoms (33% vs 82%, P = 0.01) and more co-morbid autoimmune disease (67% vs 23%, P = 0.03) when compared with patients with CD with normal IgA.

CONCLUSIONS

The prevalence of SIgAD in North American patients with CD is comparable with European data but not significantly different than control populations. Patients with CD with SIgAD exhibit decreased IgA-tTG sensitivity and lack of gastrointestinal symptoms. PIgAD is common in patients with gastrointestinal disorders but does not alter CD presentation or IgA-tTG sensitivity.

Application of Deamidated Gliadin Antibodies in the Follow-Up of Treated Celiac Disease

Introduction

The role of serological tests such as IgA anti-transglutaminase autoantibodies has become increasingly important in celiac disease (CD) diagnosis. However, the efficiency of these tests for patient follow-up is controversial. We investigated the correlation of 12 different serological tests, including recent deamidated gliadin and actin IgA tests, with villous atrophy (VA) in a retrospective cohort of treated celiac patients.

Materials and Methods

Serum samples were collected from 100 treated CD patients who had intestinal biopsy in the course of their follow-up. Antibodies against transglutaminase, deamidated gliadin peptides, and native gliadin were measured, along with IgA anti-actin. The biopsy slides were all blind-reviewed and scored according to Marsh classification.

Results

For all deamidated gliadin and transglutaminase tests, we found that a positive result was significantly associated with persistence of intestinal VA, with a diagnostic efficacy up to 80%. Furthermore, antibodies titers directly correlated with the degree of VA, indicating a strong link between disease activity and presence of antibodies in the serum. Interestingly, the tests with the highest association with persistent VA were those for deamidated gliadin IgG. Using a test positivity pattern analysis, we were also able to identify several groups of patients with distinct antibody profiles that showed significant differences in intestinal damage and diet compliance.

Conclusions

Altogether, these results show that deamidated gliadin antibodies are strongly correlated with VA and should be considered valuable tools in CD follow-up and that multiplex serologic analysis for treated CD represents a promising tool for personalized patient management.

Prevalence estimation of celiac disease in the general adult population of Latvia using serology and HLA genotyping

BACKGROUND

Prevalence estimates for celiac disease (CD) depend on the method used. The role of deamidated gliadin peptide (DGP) and genetic testing in epidemiological studies and diagnostic settings of celiac disease (CD) has still to be established.

OBJECTIVES

The objective of this article is to assess the prevalence of CD in Latvia by combining serological tests with DQ2.5/DQ8 testing.

METHODS

A total of 1444 adults from a randomly selected cross-sectional general population sample were tested by ELISA for tTG IgA, DGP IgA and IgG antibodies (QUANTA Lite®, Inova Diagnostics Inc). Samples with tTG IgA ≥20U were tested for EMA IgA by indirect immunofluorescence assay, and all specimens with tTG IgA ≥15U were tested by QUANTA-Flash® chemiluminescent assays (CIA) (Inova Diagnostics Inc) for tTG IgA, DGP IgA and IgG. DQ2.5/8 was detected in individuals with any positive ELISA test and a subgroup of controls.

RESULTS

Forty-three individuals (2.98%; 95% CI: 2.10-3.86%) tested positive by at least one ELISA test; 41.86% of the serology-positive individuals (any test above the cutoff) were DQ positive. Six individuals (0.42%; 95% CI: 0.09-0.75%) were triple ELISA positive, and DQ2.5 or DQ8 was positive in all; 0.35% (95% CI: 0.05-0.65%) were tTG IgA and EMA positive. Two tTG IgA-negative cases were both DGP IgG and IgA positive, both being DQ positive; including them in the "serology-positive" group would increase the prevalence to 0.49% (95% CI: 0.13-0.85%). CIA tests revealed 2 tTG IgA-positive and EMA-negative cases with a positive genotype. DQ2.5 or DQ8 genotype was positive in 28.6% of the serology-negative population.

CONCLUSIONS

Estimates of the prevalence of CD in Latvia based on the serogenetic testing approach range from 0.35% to 0.49% depending on the criteria used. There is a rationale for combining serological tests and DQ2.5/8 genotyping.

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.

Persistence of elevated deamidated gliadin peptide antibodies on a gluten-free diet indicates nonresponsive coeliac disease

BACKGROUND

Histologically nonresponsive coeliac disease (NRCD) is a potentially serious condition diagnosed during the follow-up of coeliac disease (CD) when patients have persistent villous atrophy despite following a gluten-free diet (GFD).

AIM

As current assessments of recovery are limited to invasive and costly serial duodenal biopsies, we sought to identify antibody biomarkers for CD patients that do not respond to traditional therapy.

METHODS

Bacterial display peptide libraries were screened by flow cytometry to identify epitopes specifically recognised by antibodies from patients with NRCD, but not by antibodies from responsive CD patients. Deamidated gliadin was confirmed to be the antigen mimicked by library peptides using ELISA with sera from NRCD (n = 15) and responsive CD (n = 45) patients on a strict GFD for at least 1 year.

RESULTS

The dominant consensus epitope sequence identified by unbiased library screening QPxx(A/P)FP(E/D) was highly similar to reported deamidated gliadin peptide (dGP) B-cell epitopes. Measurement of anti-dGP IgG titre by ELISA discriminated between NRCD and responsive CD patients with 87% sensitivity and 89% specificity. Importantly, dGP antibody titre correlated with the severity of mucosal damage indicating that IgG dGP titres may be useful to monitor small intestinal mucosal recovery on a GFD.

CONCLUSIONS

The finding of increased levels of anti-dGP IgG antibodies in CD patients on strict GFDs effectively identifies patients with NRCD. Finally, anti-dGP IgG assays may be useful to monitor mucosal damage and histological improvement in CD patients on a strict GFD.

Limited utilization of serologic testing in patients undergoing duodenal biopsy for celiac disease

Background

Clinical algorithms for the workup of celiac disease often recommend the use of serologic assays for initial screening, followed by duodenal biopsy for histologic confirmation. However, the majority of duodenal biopsies submitted to pathology for “rule out celiac” are negative. The objective of this study was to determine the underlying causes for this low diagnostic yield.

Methods

We performed a retrospective review of pathology reports from 1432 consecutive duodenal biopsies submitted for pathologic assessment to “rule out celiac” and correlated biopsy results with results for concurrent serologic testing for celiac autoantibodies.

Results

The majority of patients had no record of serologic testing prior to biopsy, and evidence of positive serology results was found in only 5% of patients. Most duodenal biopsies were submitted as part of a multi-site GI sampling strategy that included biopsies from other locations. In this context, serologic results correlated with the likelihood of significant duodenal and non-duodenal findings, and were also helpful in evaluating patients with indeterminate duodenal histology.

Conclusions

The presence of a positive screening test for celiac autoantibodies does not appear to be a major driver in the decision to submit duodenal biopsies for evaluation of celiac disease, which accounts for the low incidence of findings in these samples. In patients where celiac serology testing was performed, the results were a good predictor of the likelihood of findings on biopsy.

Defining thresholds of antibody levels improves diagnosis of celiac disease

BACKGROUND & AIMS

The European Society for Pediatric Gastroenterology and Nutrition proposed guidelines for the diagnosis of celiac disease, stating that duodenal biopsy is no longer needed if patients have symptoms and levels of immunoglobulin A anti-tissue transglutaminase (IgA anti-tTG) more than 10-fold the cut-off value. We evaluated the accuracy of this guideline in a well-characterized population using different commercial assays.

METHODS

We analyzed levels of IgA anti-tTG in serum samples from 104 consecutive pediatric and adult patients who were not deficient in IgA and were diagnosed with celiac disease from August 1, 2000, to December 31, 2009. We also analyzed serum samples from 537 consecutive patients without celiac disease (controls), collected from May 1, 2004, to October 12, 2006, who underwent intestinal biopsy analysis. Serum levels of antibodies were quantified using assays from Bio-Rad, INOVA, Genesis, and Thermo Fisher.

RESULTS

The likelihood ratio (probability of a specific result in patients divided by the probability of the same result in controls) for celiac disease increased with levels of IgA anti-tTG in all assays. Depending on the assay, the likelihood ratio for levels greater than 10-fold the cut-off value ranged from 111 to 294. The percentage of patients with celiac disease with levels of IgA anti-tTG greater than 10-fold the cut-off value ranged from 41% to 61%, depending on the assay. For levels of anti-tTG greater than 10-fold the cut-off value, the post-test probabilities for celiac disease (probability of disease, based on pretest probability and test result) were, depending on the assay, 89%-96% and 53%-75% for pretest probabilities (probability of disease depending on symptoms) of 7% and 1%, respectively.

CONCLUSIONS

To diagnose celiac disease based on serologic factors, it might be best to define thresholds for levels of IgA anti-tTG based on a predefined likelihood ratio or post-test probability, instead of a multiple of a cut-off value. Patients with a high pretest probability and levels of anti-tTG greater than 10-fold the cut-off value have a high probability for having celiac disease, aiding clinical decision making.

A proposed reference change value for an IgA anti-tissue transglutaminase immunoassay to improve interpretation of serial results in celiac patients

BACKGROUND

Celiac disease (CD) is an autoimmune disorder caused by an inappropriate immunological response to gluten ingestion in genetically susceptible individuals. IgA anti-tissue transglutaminase (tTG) antibodies have been widely employed as a specific biochemical marker for CD. Recent studies have also shown its usefulness in evaluating patient compliance with a gluten-free diet.

METHODS

A group of 28 subjects with CD was selected for the study. Each fulfilled the requirement of a gluten-free diet for more than one year. IgA anti-tTG determination was performed every two months for half a year. These data were used to estimate the biological variation (BV) of IgA anti-tTG in celiac patients and to calculate the reference change value (RCV).

RESULTS

The within-subject biological variation (CVI) and between-subject biological variation (CV(G)) were 19.2% and 75.6%, respectively, and the index of individuality was 0.25. The RCV calculated using these data together with our analytical imprecision (5.7%) was 55.5% for a 95% level of significance.

CONCLUSIONS

We have determined for the first time the BV and the RCV for IgA anti-tTG in a celiac population. This value and the probability curve generated from our data could be a valuable tool for monitoring patients' adherence to dietary treatment.

Performance of anti-deamidated gliadin peptides antibodies in celiac disease diagnosis

OBJECTIVES

To assess the usefulness of anti-deamidated gliadin peptides antibodies (a-DGP), in the diagnostic of celiac disease (CD).

PATIENTS AND METHODS

One hundred and three untreated CD patients (67 children and 36 adults) and 36 celiac patients under gluten-free diet were studied. Two hundred and seventy-four subjects served as controls (114 healthy blood donors, 80 healthy children and 80 patients with primary biliary cirrhosis). a-DGP (IgG and IgA) and anti-tissue transglutaminase antibodies (AtTG) were detected by enzyme-linked immunosorbent assay (Elisa). Anti-endomysium antibodies (AEA) were detected by indirect immunofluorescence on human umbilical cord.

RESULTS

The sensitivitiy of IgG and IgA a-DGP were 94% and 97% respectively, compared to 96% for AEA and AtTG. The specificity of a-DGP was 93.6% for IgG and 92% for IgA. The specificity of AEA and AtTG were 100%. The frequency of IgG and IgA a-DGP was significantly higher in patients with CD than in control group (94% vs. 4.4%, P<10(-7); 97% vs. 8%, P<10(-7)). The frequency of IgG a-DGP was the same in children and adult (94%). The frequency of IgA a-DGP were similar in children and adults (95.5% vs. 100%).

CONCLUSION

Our study shows that a-DGP increases neither the sensitivity nor the specificity of AEA and AtTG.

Diagnosis of celiac disease

This article reviews issues related to identifying the appropriate patient to test for celiac disease, the performance characteristics of serologic testing, the role of gene testing for human leukocyte antigen DQ2 and DQ8 haplotypes, and issues related to the performance of small intestinal biopsy. The article concludes with a review of special diagnostic considerations in pediatric patients.

Serological diagnosis of celiac disease: comparative analysis of different strategies

BACKGROUND

Different serologic tests are available for the diagnosis of celiac disease (CD).

AIM

To evaluate the diagnostic performance of anti-tissue transglutaminase (tTG) and anti-deamidated gliadin (DGP) for the serologic diagnosis of CD.

METHODS

The study population consisted of 107 consecutive adult CD and 542 consecutive disease controls who underwent an intestinal biopsy. Samples were tested for total IgA, IgA anti-tTG, and IgG anti-DGP antibodies using assays from 2 manufacturers (INOVA and Thermo Fisher). Samples were also tested by a screening assay that simultaneously detects IgA and IgG antibodies to tTG and DGP (tTG/DGP screen) (INOVA).

RESULTS

Positivity for anti-DGP or anti-tTG had a likelihood ratio for CD that varied between 20 and 115, depending on the assay. Double positivity (positive for anti-tTG and anti-DGP) had the highest likelihood ratio (≥ 215) for CD. The likelihood ratios for single positivity (positivity for one assay combined with negativity for the other) had a likelihood ratio between 0.8 and 10.1. The likelihood ratio for CD was lowest (≤ 0.12) for double negative test results. Decision tree analysis revealed that determining IgA anti-tTG and IgG anti-DGP in all patients performed better than other serologic strategies.

CONCLUSIONS

The use of likelihood ratios improves the clinical interpretation of serologic testing for CD. Double positive test results had the highest likelihood ratio for CD, whereas double negative test results had the lowest likelihood ratio.

Diagnostic value of anti-deamidated gliadin peptide IgG antibodies for celiac disease in children and IgA-deficient patients

OBJECTIVES

The aim of the study was to analyze the diagnostic performance of anti-deamidated gliadin peptide (dGp) immunoglobulin (Ig) G and IgA regarding the age at celiac disease (CD) diagnosis and the anti-dGp IgG usefulness for diagnosing CD IgA-deficient patients.

METHODS

Anti-dGp IgG and IgA and anti-native gliadin (nGlia) IgA were determined by enzyme fluoroimmunoassay in 100 newly diagnosed anti-tissue transglutaminase (tTG) IgA-positive pediatric and adult patients with CD and in 100 age-matched patients with other digestive pathologies. Anti-dGp IgG was evaluated in 6 CD IgA-deficient patients.

RESULTS

When analyzing all of the patients, the anti-dGp IgG assay showed higher diagnostic accuracy (area under receiver operating characteristic curve), specificity, and positive predictive value than anti-dGp IgA and anti-nGlia IgA. All of the diagnostic parameters corresponding to anti-dGp IgG reached the same values as anti-tTG IgA in children 7 years or younger. In older patients, both anti-dGp isotypes showed an inverse behavior, IgG having a higher specificity and positive predictive value but a lower sensitivity and negative predictive value than IgA. Anti-dGp levels were associated with the severity of intestinal lesions, and an inverse association was found regarding age at diagnosis. Both anti-dGp IgG and IgA were found to be positive in the 9 patients with minimal intestinal changes included in the study. All of the patients with CD with IgA deficiency were positive for anti-dGp IgG.

CONCLUSIONS

The diagnostic performance of anti-dGp depends on the antibody isotype and on the age at CD diagnosis, anti-dGp IgG being a serological marker at least as useful as anti-tTG IgA for detecting CD in children ages 7 years or younger. Our data also indicate that anti-dGp IgG can improve the diagnosis of IgA-deficient patients.

IgA antibodies against deamidated gliadin peptides in patients with chronic liver diseases

BACKGROUND/AIMS

IgA antibodies against tissue-transglutaminase (anti-tTG-IgA) and IgA and IgG antibodies against deamidated gliadin peptides (anti-DGP-IgA and anti-DGP-IgG) are considered specific for celiac disease (CD) whereas, patients with chronic liver disorders have an increased risk of latent CD development. We investigated the prevalence and clinical significance of anti-DGP-IgA, anti-DGP-IgG and anti-tTG-IgA in a large cohort of patients with chronic liver diseases.

METHODS

668 patients without gastrointestinal symptoms (426 viral hepatitis, 94 autoimmune liver diseases, 61 alcoholic disease, 46 non-alcoholic fatty liver disease, 41 with other liver disorders) were investigated by ELISAs (INOVA Diagnostics). Patients positive for at least one autoantibody invited for a small-intestinal biopsy and HLA-DQ typing.

RESULTS

Anti-DGP-IgA were detected in 8.5%, anti-DGP-IgG in only one (0.15%, P<0.001) and anti-tTG-IgA in 5.8% of patients (P=0.05). Fifty-two were anti-DGP-IgA(+)/anti-tTG-IgA(-), 34 anti-DGP-IgA(-)/anti-tTG-IgA(+), and 5 anti-DGP-IgA(+)/anti-tTG-IgA(+). Anti-DGP-IgA positivity was associated with older age (P<0.05), cirrhosis (P<0.05) and increased IgA (P<0.05) whereas, anti-tTG-IgA only with cirrhosis (P<0.05). Histology and HLA-typing compatible with CD was revealed in 4/14 anti-DGP-IgA(+)/anti-tTG-IgA(-), 0/13 anti-DGP-IgA(-)/anti-tTG-IgA(+) and 2/2 anti-DGP-IgA(+)/anti-tTG-IgA(+). All 6 patients diagnosed with CD were anti-DGP-IgA(+) and only 2 anti-tTG-IgA(+).

CONCLUSIONS

Although a significant number of patients had detectable CD-related autoantibodies, anti-DGP-IgA test seems better than anti-tTG-IgA for unmasking occult forms of CD in patients with chronic liver disorders. The known good performance for CD diagnosis of anti-DGP-IgG test was not confirmed in this specific group of patients.

Design of a peptide for immunodetection of IgA antigliadin antibody for the purpose of screening of celiac disease

Celiac disease (CD) is gluten induced enteropathy which requires jejunal biopsy for diagnosis. To select the patients for endoscopoic procedure some serologic tests are popular in clinical practice for screening of CD. Although gliadin is one of the key immuno activator of the disease; serological screening by immuno-detection of gliadin is not recommended. In this context we have designed a peptide using tools of computational biology keeping molecular pathogenesis of the disease into consideration such that antigliadin antibody detection based sensitive and specific cost effective tool for screening of celiac disease can be developed. The designed peptide QPFPEP interacts in a stable manner with dimeric immunoglobin A1 molecule and its parent peptide QPFPQP are sequentially present in maximum number of gliadin epitopes. This hexapeptide is predicted to interact with dimeric IgA1, which increases in the biofluids of the CD patients.

ABBREVIATIONS

CD - Celiac disease, TT - Tissue transglutamase, IgA - Immunoglobulin A, AGA - antigliadin antibody, Immunoglobulin G - IgG.

Improving serological test ordering patterns for the diagnosis of celiac disease through clinical laboratory audit of practice

BACKGROUND

Clinical Practice Guidelines (CPG) from both adult medicine and pediatrics recommend tTG to screen for celiac disease (CD).

DESIGN AND METHODS

Serological test orders for celiac disease were evaluated against the guidelines. Ordering physicians were categorized as gastroenterologists, immunologists, pediatricians, other hospital physicians and non-hospital physicians. Interventions based on initial audit were implemented, including interacting with physicians, revising test menu and changing test ordering policy. After implementation of interventions, test orders were re-evaluated.

RESULTS

After corrective interventions celiac panel (CP) orders were decreased from 48.4% to 3.6% in children, and from 72.3% to 28.1% in adults. Physicians ordered tTG alone for more than 90% of children. In adults the ordering of tTG alone was significantly increased from 7.2% to 61.3% (from 8.9% to 63.9% for gastroenterologists and from 8.1% to 44.4% for other physicians (p<0.05)).

CONCLUSIONS

The audit reduced the CPG-practice gap that existed in the screening of CD.

Screening for unrecognized coeliac disease in subfertile couples

OBJECTIVE

Subfertility has been reported as a long-term complication of unrecognized and/or untreated coeliac disease (CD); however, the results from studies on this topic are ambiguous. We aimed to determine the prevalence of unrecognized CD in subfertile male-female couples visiting a fertility clinic compared with the general population.

METHODS

Subjects included 1038 male-female couples (n = 2076) who visited the fertility clinic of the Leiden University Medical Center in the Netherlands between 2003 and 2009. All consecutive patients were routinely, serologically screened, and those with positive test results for antibodies against IgA anti-tissue transglutaminase type 2 and IgA endomysial antibodies were considered to have unrecognized CD. Clinical data on gender, age, height, weight, diagnosis of subfertility, and previously diagnosed CD were collected from the clinical files. Subsequently, after serological screening, all patients were anonymized. The prevalence of unrecognized CD was compared with the one in the general adult population in the Netherlands (0.35%).

RESULTS

The prevalence of unrecognized CD in subfertile male-female couples was 0.48% (10/2076; 6 females and 4 males) and was not significantly more frequent compared with the general population. Compared with the control group, similar CD prevalences were found within the different subfertility categories separately: unexplained subfertility, anovulation, tubal pathology, and male factor (p = NS).

CONCLUSION

In our large study cohort of subfertile male-female couples, the prevalence of unrecognized CD is comparable to the general population in the Netherlands. No association was observed between CD and subfertility in the different subfertility categories and genders.

Assessment of a combination screening assay for celiac disease

PURPOSE

A serological screening assay for celiac disease (CD), designed to simultaneously detect IgA and IgG anti-tissue transglutaminase (a-tTG) and IgA and IgG deamidated gliadin peptide antibodies (a-DGP), was recently developed. In this study, we establish the performance of this assay.

METHODS

We enrolled 41 CD patients and 18 CD patients on gluten-free diets. The diagnosis of CD was based on histological and serological criteria, including concomitant positive serology tests (a-tTG, IgA anti-endomysial antibodies). As control population, we enrolled 169 subjects: 145 disease controls and 24 blood donors. In all cases, serum samples were tested for: IgA a-tTG, IgG a-tTG, IgA a-DGP, IgG a-DGP, IgA anti-endomysial antibodies (EMA), IgA and IgG for a-tTG and a-DGP in a single assay.

RESULTS

The new test, QUANTA Lite (™) h-tTG/DGP Screen, detects all IgA and IgG antibodies against atTG and a-DGP present in a sample. In our study, the test showed 100% sensitivity and 91.12% specificity.

CONCLUSIONS

This study showed additional value of the new h-tTG/DGP Screen assay, which proved superior to more conventional assays and can be considered the best initial test for CD. Further studies are necessary to determine whether combination of h-tTG/DGP Screen with IgA a-tTG or IgA a-DGP can be used to obviate the need for duodenal biopsy in high- and low-risk populations.

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.

Testing for gluten-related disorders in clinical practice: the role of serology in managing the spectrum of gluten sensitivity

Immunoglobulin A tissue transglutaminase is the single most efficient serological test for the diagnosis of celiac disease. It is well known that immunoglobulin A tissue transglutaminase levels correlate with the degree of intestinal damage, and that values can fluctuate in patients over time. Serological testing can be used to identify symptomatic individuals that need a confirmatory biopsy, to screen at-risk populations or to monitor diet compliance in patients previously diagnosed with celiac disease. Thus, interpretation of serological testing requires consideration of the full clinical scenario. Antigliadin tests are no longer recommended for the diagnosis of classical celiac disease. However, our understanding of the pathogenesis and spectrum of gluten sensitivity has improved, and gluten-sensitive irritable bowel syndrome patients are increasingly being recognized. Studies are needed to determine the clinical utility of antigliadin serology in the diagnosis of gluten sensitivity.

Novel trends in celiac disease

Celiac disease (CD) is one of the most common food intolerances in developed world. It affects genetically susceptible individuals and has severe consequences if it remains undiagnosed. A disease known for more than a century, it is still the focus for experts from various fields of research and development. Geneticists, pathologists, immunologists, food engineers and dieticians share their knowledge and expertise to improve the conditions of CD patients. With new insights in the pathomechanism of gluten processing and antigen presentation in CD, it was possible to improve the diagnostic antigen mimicking the primary epitope in CD. These celiac neo-epitopes are comprised of a complex of gliadin peptides crosslinked with transglutaminase (tTg). They are an early diagnostic marker for CD which occurs up to 6 months earlier than classical markers known to miss a certain amount of CD patients.

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.