An update on the diagnostics of celiac disease

In celiac disease, highly sensitive and specific serum endomysial and transglutaminase 2 antibody tests are widely used in identifying patients for diagnostic endoscopy and small-bowel biopsy. In addition, the recently developed deamidated gliadin peptide antibody tests show promise in celiac disease diagnostics. In view of these apparent problems attending the diagnostic gold standard, gluten-induced small-bowel mucosal villous atrophy with crypt hyperplasia, other diagnostic approaches beyond conventional histology have been introduced. Furthermore, the diagnostic criteria for celiac disease are currently under revision with an eye also to noninvasive diagnostic strategies.     

Antibodies in celiac disease: implications beyond diagnostics

Celiac disease is a multisystemic dietary, gluten-induced autoimmune disorder characterized by the presence of transglutaminase (TG) 2 serum autoantibodies. Distinct autoantibodies targeting members of the TG family (TG2, TG3 and TG6) are found deposited in small-bowel mucosa and in extraintestinal tissues affected by the disease. Serum autoantibodies against other self-antigens also emerge in untreated celiac disease patients. Although villous atrophy and crypt hyperplasia in small-bowel biopsy samples are still the gold standards in diagnostics, celiac disease-specific antibodies are widely used as diagnostic aids. Gluten-induced small-bowel mucosal T-cell response is the cornerstone in the pathogenesis of the disorder, but humoral immunity may also play a central role. This review article is focused on the autoantibodies that occur in the context of celiac disease. The article summarizes the diagnostic utility of different celiac-related antibodies and discusses their roles in the pathogenesis of the disease.     

Serodiagnostic Assays for Celiac Disease Based on the Open or Closed Conformation of the Autoantigen,Transglutaminase 2

The autoantigen of celiac disease, transglutaminase 2 (TG2), adopts an open conformation during enzymatic activation. We studied diagnostic accuracy of serodiagnostic assays using TG2 in its open and closed conformation as antigens in patients with diagnostic difficulties. The open TG2 antibody (TG2ab) test identified 93% of untreated celiac patients in contrast to 44%, 27%, and 68% detected by closed and conventional TG2ab and endomysial antibody (EmA) tests, respectively. The assay was able to detect 60% of non-responding celiac patients seronegative for conventional TG2ab and EmA. The titers of the openTG2abs were higher than those of the closed TG2abs. The serological test utilizing TG2 in an open conformation was more accurate than the other assays in finding active celiac disease even in patients having negative or borderline conventional celiac autoantibodies and in revealing poor dietary response non-invasively. It thus offers a promising tool in the diagnostics and follow-up of celiac disease.     

Adenocarcinoma of jejunum in association with nontropical sprue

A variety of small-bowel malignant neoplasms have been reported in association with nontropical sprue (celiac disease). Lymphomas have been the most common malignant neoplasms to complicate this disease. However, adenocarcinoma of the small bowel has infrequently been reported. The suggestion has been made that patients with nontropical sprue are at increased risk for developing small-bowel adenocarcinoma. Three additional cases of small-bowel adenocarcinoma in association with nontropical sprue are reported.     

Serologic testing for celiac disease in the United States: results of a multilaboratory comparison study

The aim of this study was to compare the efficiencies of six reference laboratories for serologic testing for celiac disease. Serum from 20 patients with untreated celiac disease and from 20 controls was thawed, divided, and distributed to each participating laboratory, which performed endomysial antibody tests. Five laboratories also performed antigliadin antibody tests. Sensitivity for endomysial antibody immunoglobulin A (IgA) varied from 57 to 90%. In all laboratories, the specificity for celiac disease was 100%. The sensitivity and specificity for both IgA and IgG antigliadin antibody varied significantly. When results from all three tests were combined in each laboratory, sensitivity was 90 to 100%. The specificity for endomysial antibody was 100% in the laboratories. Sensitivity was less than reported previously. Standardization of these tests is needed in the United States.     

Serologic Testing for Celiac Disease in the United States: Results of a Multilaboratory Comparison Study

The aim of this study was to compare the efficiencies of six reference laboratories for serologic testing for celiac disease. Serum from 20 patients with untreated celiac disease and from 20 controls was thawed, divided, and distributed to each participating laboratory, which performed endomysial antibody tests. Five laboratories also performed antigliadin antibody tests. Sensitivity for endomysial antibody immunoglobulin A (IgA) varied from 57 to 90%. In all laboratories, the specificity for celiac disease was 100%. The sensitivity and specificity for both IgA and IgG antigliadin antibody varied significantly. When results from all three tests were combined in each laboratory, sensitivity was 90 to 100%. The specificity for endomysial antibody was 100% in the laboratories. Sensitivity was less than reported previously. Standardization of these tests is needed in the United States.     

Update on the evaluation and diagnosis of celiac disease

PURPOSE OF REVIEW: Our understanding of the pathophysiology of celiac disease has advanced with associated improvement in diagnostic modalities. Recent studies have placed the prevalence of celiac disease in Western populations at between 1:250 and 1:67. Celiac disease is common throughout the world and most cases go undiagnosed. Understanding the risk factors, clinical presentations and diagnostic modalities is necessary to identify and treat patients with this commonly misdiagnosed disorder. RECENT FINDINGS: Increased prevalence of celiac disease in individuals with autoimmune diseases, reduced bone mineral density and undiagnosed liver disease have been confirmed. However, celiac disease may not be associated with Down's syndrome or epilepsy. Evidence supports high sensitivity and specificity of endomysial- and tissue transglutaminase-based tests in most settings. In children, high or low tissue transglutaminase levels may preclude the need for duodenal biopsy. Cost-effectiveness studies suggest using tissue transglutaminase or endomysial initially, while distal duodenal or jejunal biopsy may confirm celiac disease in the absence of proximal changes. SUMMARY: There is insufficient evidence to support mass screening for celiac disease. However, case finding in individuals with risk factors for celiac disease is recommended. Further study is necessary to define diagnostic algorithms and target populations likely to benefit from testing.     

Galactosylation of Serum IgA1 <Emphasis Type="Italic">O</Emphasis>-Glycans in Celiac Disease

In celiac disease, gluten ingestion provokes small-bowel mucosal injury and production of IgA autoantibodies against transglutaminase 2 (TG2). It has been suggested that in celiac patients IgA could mediate the transepithelial passage of gluten peptides in a mechanism involving the transferrin receptor. As IgA1 with galactose-deficient O-linked glycans has elevated affinity for the transferrin receptor, we assessed whether total serum IgA1 and IgA1 anti-TG2 autoantibodies in celiac patients are aberrantly glycosylated. We report that males with celiac disease have higher total serum levels of galactose-deficient IgA1 than non-celiac males. Furthermore, O-glycans of the disease-specific TG2 IgA1 autoantibodies in celiac patients exhibited elevated galactose deficiency. A gluten-free diet had no effect on the total serum levels of galactose-deficient IgA1, whereas the amount of galactose-deficient anti-TG2 IgA1 decreased. Thus, the undergalactosylated IgA1 molecules are not pathognomonic for celiac disease, but galactose deficiency in IgA1 could be an aggravating factor.     

Diagnosis and classification of celiac disease and gluten sensitivity

Celiac disease is a complex disorder, the development of which is controlled by a combination of genetic (HLA alleles) and environmental (gluten ingestion) factors. New diagnostic guidelines developed by ESPGHAN emphasize the crucial role of serological tests in the diagnostic process of symptomatic subjects, and of the detection of HLA DQ2/DQ8 alleles in defining a diagnosis in asymptomatic subjects belonging to at-risk groups. The serological diagnosis of CD is based on the detection of class IgA anti-tissue transglutaminase (anti-tTG) and anti-endomysial antibodies. In patients with IgA deficiency, anti-tTG or anti-deamidated gliadin peptide antibody assays of the IgG class are used. When anti-tTG antibody levels are very high, antibody specificity is absolute and CD can be diagnosed without performing a duodenum biopsy. Non-celiac gluten sensitivity is a gluten reaction in which both allergic and autoimmune mechanisms have been ruled out. Diagnostic criteria include the presence of symptoms similar to those of celiac or allergic patients; negative allergological tests and absence of anti-tTG and EMA antibodies; normal duodenal histology; evidence of disappearance of the symptoms with a gluten-free diet; relapse of the symptoms when gluten is reintroduced.     

Prevalence and clinical characteristics of celiac disease in Downs syndrome in a US study.

Celiac disease is an autoimmune gastrointestinal disorder characterized by mucosal atrophy of the jejunum on exposure to gluten, a protein found in grains. The purpose of our study was to determine the prevalence of celiac disease in children with Downs syndrome in a U.S.-based Caucasian population. The 97 Downs syndrome children were screened for celiac disease using serum IgA-anti-endomysial antibody testing, which is highly specific and sensitive for the disorder. Children with titers greater than 1:5 (using the IgA endomysial antibody [EMA] test; EMA+) were considered affected. Ten children (10.3%) were EMA+. We examined their HLA DQA1 DQB1 genotype, karyotype, clinical characteristics, and the prevalence of celiac disease in their first-degree relatives. The nine available karyotypes were trisomy 21. Downs syndrome-specific mean height percentile was 64%+/-26% (range <5-99%) and weight percentile was 43%+/-28% (range 5-95%). Presence of diarrhea, constipation, vomiting, and abdominal pain was similar for children with and without celiac disease. Only bloating symptoms were significantly more frequent in those with celiac disease (EMA+). Seven of eight (88%) genotyped EMA+ children had the celiac disease-associated high-risk HLA DQA1*0501 DQB1*0201 genotype as compared with 13/ 80 (16%) of EMA- children. Five of 48 (10%) first-degree relatives of the celiac disease (EMA+) children were EMA+. In conclusion, celiac disease, as diagnosed by positive endomysial antibody tests, has an increased prevalence in children with Downs syndrome in the U.S. as compared with the general population (1/250). Clinical and growth characteristics do not distinguish between children with and without celiac disease. Based on these observations, it is recommended that children with Downs syndrome be screened for celiac disease.     

Contribution of celiac disease autoantibodies to the disease process

Transglutaminase 2 is a multifunctional protein involved in cellular adhesion. Moreover, transglutaminase 2 has been identified as the autoantigen in celiac disease, and in untreated celiac disease, in addition to being present in the serum, the transglutaminase 2-targeted autoantibodies are bound to their antigen in the basement membrane underlining the small-bowel mucosal epithelium. Furthermore, the disease-specific transglutaminase 2-targeted autoantibodies have been experimentally shown to exert various biological effects on different cell types. Using Caco-2 intestinal epithelial cells, it has now also been demonstrated that serum transglutaminase 2-targeted autoantibodies from untreated celiac patients inhibit the adhesion of these cells. These findings provide an important direction for future research to improve our general understanding of celiac disease pathogenesis and especially the role of the disease-specific autoantibodies during the progression of the disorder.     

Tissue transglutaminase antibody determination in celiac disease. Analysis of diagnostic specificity of anti-human IgA-type assays

Biopsy is onerous and, for this reason, immunodiagnostics in sera of celiac disease patients are an "additional diagnostic standard." The objective of the study was to investigate the variability in diagnostic specificity of ELISAs for the detection of IgA anti-tissue transglutaminase antibodies in serum of celiac disease patients who underwent biopsy. All patients were included in the study on the basis that they had a small intestinal biopsy. We studied 18 patients with histological proven celiac disease (7 male, 11 female, mean age +/- SD: 35+/-19 years) from Graz, Austria. Healthy control subjects were also entered into the study. The determinations of the anti-tissue transglutaminase antibodies were simultaneously performed together with the endomysium and gliadin antibody markers. We analysed the 216 serum values according to Cochran's non-parametric Q-test. The complexity to the analysis reflects the complexity of the diagnostic situation with the patients. No real differences were found in the reactions of the anti-human IgA-type anti-tissue transglutaminase ELISAs. Based on these results, an association was established between the outcomes of anti-human IgA-type ELISAs for the specific antigen and patients with histologically proven celiac disease, treated for celiac disease after histology was carried out and the diagnosis was made, and healthy controls. The detection of IgA anti-tissue transglutaminase antibodies in serum is a promising alternative to the indirect immunofluorescence determination of IgA-type endomysium antibodies. One ELISA for the specific antigen showed some advantage with respect to its extended scale of detection. Immunopathology of celiac disease can be based on the results of the appropriate IgA anti-tissue transglutaminase ELISAs under uncomplicated gastrointestinal conditions.     

Seronegative autoimmune diseases: A challenging diagnosis

Autoimmune diseases (AID) are increasingly prevalent conditions which comprise more than 100 distinct clinical entities that are responsible for a great disease burden worldwide. The early recognition of these diseases is key for preventing their complications and for tailoring proper management. In most cases, autoantibodies, regardless of their potential pathogenetic role, can be detected in the serum of patients with AID, helping clinicians in making a definitive diagnosis and allowing screening strategies for early -and sometimes pre-clinical- diagnosis. Despite their undoubted crucial role, in a minority of cases, patients with AID may not show any autoantibody, a condition that is referred to as seronegative AID. Suboptimal accuracy of the available laboratory tests, antibody absorption, immunosuppressive therapy, immunodeficiencies, antigen exhaustion, and immunosenescence are the main possible determinants of seronegative AID. Indeed, in seronegative AID, the diagnosis is more challenging and must rely on clinical features and on other available tests, often including histopathological evaluation and radiological diagnostic tests. In this review, we critically dissect, in a narrative fashion, the possible causes of seronegativity, as well as the diagnostic and management implications, in several AID including autoimmune gastritis, celiac disease, autoimmune liver disease, rheumatoid arthritis, autoimmune encephalitis, myasthenia gravis, Sjögren’s syndrome, antiphospholipid syndrome, and autoimmune thyroid diseases.     

Prevalence and clinical characteristics of celiac disease in Downs syndrome in a U.S. study

Celiac disease is an autoimmune gastrointestinal disorder characterized by mucosal atrophy of the jejunum on exposure to gluten, a protein found in grains. The purpose of our study was to determine the prevalence of celiac disease in children with Downs syndrome in a U.S.‐based Caucasian population. The 97 Downs syndrome children were screened for celiac disease using serum IgA‐anti‐endomysial antibody testing, which is highly specific and sensitive for the disorder. Children with titers greater than 1:5 (using the IgA endomysial antibody [EMA] test; EMA+) were considered affected. Ten children (10.3%) were EMA+. We examined their HLA DQA1 DQB1 genotype, karyotype, clinical characteristics, and the prevalence of celiac disease in their first‐degree relatives. The nine available karyotypes were trisomy 21. Downs syndrome‐specific mean height percentile was 64% ± 26% (range <5–99%) and weight percentile was 43% ± 28% (range 5–95%). Presence of diarrhea, constipation, vomiting, and abdominal pain was similar for children with and without celiac disease. Only bloating symptoms were significantly more frequent in those with celiac disease (EMA+). Seven of eight (88%) genotyped EMA+ children had the celiac disease‐associated high‐risk HLA DQA1*0501 DQB1*0201 genotype as compared with 13/80 (16%) of EMA− children. Five of 48 (10%) first‐degree relatives of the celiac disease (EMA+) children were EMA+. In conclusion, celiac disease, as diagnosed by positive endomysial antibody tests, has an increased prevalence in children with Downs syndrome in the U.S. as compared with the general population (1/250). Clinical and growth characteristics do not distinguish between children with and without celiac disease. Based on these observations, it is recommended that children with Downs syndrome be screened for celiac disease. © 2001 Wiley‐Liss, Inc.     

Contribution of celiac disease autoantibodies to the disease process

Evaluation of: Teesalu K, Panarina M, Uibo O, Uibo R, Utt M. Autoantibodies from patients with celiac disease inhibit transglutaminase 2 binding to heparin/heparan sulfate and interfere with intestinal epithelial adhesion. Amino Acids doi:10.1007/s00726-011-1020-1 (2011) (Epub ahead of print).

Transglutaminase 2 is a multifunctional protein involved in cellular adhesion. Moreover, transglutaminase 2 has been identified as the autoantigen in celiac disease, and in untreated celiac disease, in addition to being present in the serum, the transglutaminase 2-targeted autoantibodies are bound to their antigen in the basement membrane underlining the small-bowel mucosal epithelium. Furthermore, the disease-specific transglutaminase 2-targeted autoantibodies have been experimentally shown to exert various biological effects on different cell types. Using Caco-2 intestinal epithelial cells, it has now also been demonstrated that serum transglutaminase 2-targeted autoantibodies from untreated celiac patients inhibit the adhesion of these cells. These findings provide an important direction for future research to improve our general understanding of celiac disease pathogenesis and especially the role of the disease-specific autoantibodies during the progression of the disorder.     

Celiac disease and endocrine autoimmunity – the genetic link

Celiac disease is a small intestinal inflammatory disease with autoimmune features that is triggered and maintained by the ingestion of the storage proteins (gluten) of wheat, barley and rye. The prevalence of celiac disease is increased in patients with monoglandular and/or polyglandular autoimmunity and their relatives. Between 10 and 30% of patients with celiac disease are thyroid and/or type 1 diabetes antibody positive, while around 5 to 7% of patients with autoimmune thyroid disease and/or type 1 diabetes are IgA anti-tissue transglutaminase antibody positive. The close relationship between celiac disease and endocrine autoimmunity is largely explained by sharing a common genetic background. The HLA antigens DQ2 (DQA1*0501-DQB1*0201) and/or DQ8 (DQA1*0301-DQB1*0302), that are tightly linked to DR3 and DR4, respectively, are the major common genetic predisposition. Moreover, functional single nucleotide polymorphisms of various genes that are involved in immune regulation have been identified as “overlap” susceptibility genes for both celiac disease and monoglandular or polyglandular autoimmunity. While plausible, it remains to be established how far a gluten free diet may prevent or ameliorate glandular autoimmunity. In conclusion, all patients with celiac disease should be screened for type 1 diabetes and/or autoimmune thyroid disease. Conversely, patients with the above autoimmune endocrine disorders should be also screened for celiac disease.     

Serological testing for celiac disease in women undergoing assisted reproduction techniques

BACKGROUND: The assertion of a causal relationship between celiac disease and infertility is suggested by several lines of research. Nevertheless, robust evidence has not yet been provided. The present study evaluated, for the first time, the prevalence of celiac disease in women undergoing assisted reproduction techniques (ART). METHODS: Serum samples from 200 Italian women undergoing ART were evaluated for celiac disease by endomisium antibody (EMA) and transglutaminase antibody (t-TGA)-two highly sensitive and specific serological markers. Two hundred women not reporting reproductive problems and having delivered at least one child served as controls. In cases of positive serology, the diagnosis was confirmed by jejunal biopsy. RESULTS: Five (2.5%) women from the study group and two (1.0%) from the control group were found to have celiac disease (P = 0.44). The main indications for ART in women found to have celiac disease were tubal factor in two cases and male infertility in three cases. None of these women reported major gastrointestinal complaints. Extra intestinal signs linked to celiac disease were noted in four out of five patients. CONCLUSION: This study raises the issue of celiac disease screening in ART programmes. Given the available evidence in the literature combined with our observations from this study, the value of serological testing for celiac disease in infertile women remains uncertain. Further studies to address this issue are required.     

Histopathological diagnosis of celiac disease in adults with functional dyspeptic syndrome

Celiac disease is associated with permanent intolerance to gluten, which is found in some cereals. The symptoms of the disease are often nonconspicuous and the course of the disease is atypical. With the introduction of serological markers as a sensitive method of testing new cases of the disease were identified. Despite of the increased screening intensity among children and adults celiac disease in our region is still underdiagnosed. The article deals with the diagnostics of celiac disease in adults with functional dyspeptic syndrome. It is based on the laboratory and pathological correlation of 25 patients. Our aim was to identify the group at risk with functional dyspeptic syndrome and celiac disease. This disease can show symptoms from the onset all the way to relapse. Each person was examined by a gastroenterologist while hospitalized in the relevant department. In addition to the routine serological testing, blood samples were taken and sent for antiendomyzial antibody testing for positive reaction verification. A subsequent gastrointestinal examination was done and samples taken from the duodenum were sent for histology. Light microscopy analysis showed mucous damage typical for celiac disease, which is expressed with the levels of the Marsh histological grading. In closing, we recommend a three-step approach to goal-oriented screening of celiac disease. Determination of autoantibody against tissue transglutaminase, if positive, then biopsy from the aboral duodenum, and consequently follow-up by testing for antiendomyzial antibody.     

Serologic screening for celiac disease in children: a comparison between established assays and tests with deamidated gliadin‐derived peptides plus conjugates for both IgA and IgG antibodies

Selection of patients for diagnostic biopsy concerning celiac disease (CD) is mainly guided by the results with serological screening tests like anti‐tissue‐transglutaminase (tTG), anti‐endomysium (EmA) and anti‐gliadin (AGA) IgA. New tests using deamidated gliadin‐derived peptides (DGP) including both IgA and IgG antibodies have been developed, to cover the IgA‐deficient sera. In addition, a combined IgA and IgG DGP test, with or without human erythrocyte‐derived tTG, offers possible advantages. In order to explore the screening accuracy of the new combination tests sera from 167 children below 3 years of age were assayed. Biopsy had been taken in connection with serology in 32 of these children, 24 with histopathological CD. The results with the DGP and the combined test were congruent with the IgA antibody tests for tTG, EmA and AGA, all identifying 21 of 24 of the CD cases. Two of the CD patients were AGA‐IgA positive only (2/24), while 2 of 24 sera were AGA–IgA negative but positive in all the other tests. These results raises the question whether the modifications of the gliadin antigen not only decrease false positivity but also give more false‐negative results, a major drawback for a screening test for an important disease. Further studies have to be undertaken to explore this. Our results also stress that serologic screening of CD in children cannot be based on one test only.     

Fatal CNS vasculopathy in a patient with refractory celiac disease and lymph node cavitation

Celiac disease is an enteropathy occurring in genetically predisposed individuals due to a dietary intolerance to gluten. Patients with celiac disease may develop a neurological disorder of unknown cause, although autoimmune mechanisms are suspected. We report on a 56-year-old man with celiac disease, who became refractory to a gluten-free diet and died of a rapidly progressive encephalopathy. Magnetic resonance imaging indicated focal lesions of the cerebellum and brainstem, and electrodiagnostic studies suggested an axonal neuropathy. Autopsy revealed a flattened small-bowel mucosa with intraepithelial lymphocytosis, a spectrum of degenerative changes of the intra-abdominal and mediastinal lymph nodes, including cavitary degeneration, and splenomegaly. Histologically, the lymph nodes showed pseudocyst formation and lymphocytic vasculitis with fibrinoid necrosis, and sections of the brain exhibited fibrinoid degeneration of small blood vessels, sparse perivascular lymphocytic infiltrates, and perivascular ischemic lesions. Identical T-cell clones were identified in the duodenum, stomach, lymph nodes, and spleen. This patient had an unusual neurological disorder related to a vasculopathy, probably mediated by a circulating neoplastic clone of activated T cells.