Antibody and genetic testing in coeliac disease

Meta-Analysis and Systematic Review of HLA DQ2/DQ8 in Adults with Celiac Disease

Although people with human leukocyte antigens (HLA) DQ2 and/or DQ8 are more likely to develop celiac disease (CD), the condition cannot be fully explained by this genetic predisposition alone. Multiple, as yet unidentified, factors contribute to the genesis of CD, including genetics, the environment, and the immune system. In order to provide insight into a prospective possibility and an expanded screening technique, we aim to undertake a comprehensive and meta-analytical study of the assessment and distribution of HLA class II (HLA-DQ2/DQ8) in adult CD patients. A systematic review was conducted using an electronic search of databases (PubMed, Google Scholar, Embase, and Direct Science) from January 2004 to February 2022. DQ2/DQ2 homozygotes have the highest risk of developing CD. DQ2/DQ8 typing is an effective test to exclude CD from the differential diagnosis of a patient with CD symptoms. Although other non-HLA genes have been associated with CD, they are rarely considered at diagnosis because they account for only a small proportion of the heritability of CD. This finding, together with the information gathered previously, may be useful in considering widely available and economically feasible screening options for celiac disease in young people.

Experiences and own management regarding residual symptoms among people with coeliac disease

CONTEXT

Between 7% and 30% of people with treated coeliac disease suffer from residual symptoms, and there is a knowledge gap about their own management of these symptoms.

AIM

To explore experiences and management concerning residual symptoms despite a gluten-free diet in people with coeliac disease.

METHODS

A qualitative explorative design with semi-structured interviews with 22 adults with coeliac disease in Sweden. Data were analysed using qualitative content analysis.

RESULTS

The informants had, at diagnosis, thought that their symptoms would disappear if they followed a gluten-free diet, but the disease was continuing to have a substantial impact on their lives, despite several years of treatment. They experienced cognitive, somatic as well as mental symptoms, including impact on personality (e.g. having a "shorter fuse", being more miserable or tired). However, only a few informants had sought medical care for persistent symptoms. Instead they tried to manage these by themselves, e.g. abstaining from food during periods of more intense symptom, or using distraction. The management of persistent symptoms resembled thorough detective work. To prevent problems related to residual symptoms the informants used withdrawal of social contact as well as acceptance of their situation.

CONCLUSION

People with treated coeliac disease may experience residual symptoms of both a physical and psychological nature, causing major negative impacts on their lives in different ways. In the light of this, healthcare staff should change their practices regarding the follow-up of these people, and in addition to medical care should provide guidance on management strategies to facilitate the daily life. Furthermore, information to newly diagnosed persons should make them aware of the possibility to experience continued symptoms, despite treatment.

Accurate and robust genomic prediction of celiac disease using statistical learning

Practical application of genomic-based risk stratification to clinical diagnosis is appealing yet performance varies widely depending on the disease and genomic risk score (GRS) method. Celiac disease (CD), a common immune-mediated illness, is strongly genetically determined and requires specific HLA haplotypes. HLA testing can exclude diagnosis but has low specificity, providing little information suitable for clinical risk stratification. Using six European cohorts, we provide a proof-of-concept that statistical learning approaches which simultaneously model all SNPs can generate robust and highly accurate predictive models of CD based on genome-wide SNP profiles. The high predictive capacity replicated both in cross-validation within each cohort (AUC of 0.87–0.89) and in independent replication across cohorts (AUC of 0.86–0.9), despite differences in ethnicity. The models explained 30–35% of disease variance and up to ∼43% of heritability. The GRS's utility was assessed in different clinically relevant settings. Comparable to HLA typing, the GRS can be used to identify individuals without CD with ≥99.6% negative predictive value however, unlike HLA typing, fine-scale stratification of individuals into categories of higher-risk for CD can identify those that would benefit from more invasive and costly definitive testing. The GRS is flexible and its performance can be adapted to the clinical situation by adjusting the threshold cut-off. Despite explaining a minority of disease heritability, our findings indicate a genomic risk score provides clinically relevant information to improve upon current diagnostic pathways for CD and support further studies evaluating the clinical utility of this approach in CD and other complex diseases.

Celiac disease (CD) is a common immune-mediated illness, affecting approximately 1% of the population in Western countries but the diagnostic process remains sub-optimal. The development of CD is strongly dependent on specific human leukocyte antigen (HLA) genes, and HLA testing to identify CD susceptibility is now commonly undertaken in clinical practice. The clinical utility of HLA typing is to exclude CD when the CD susceptibility HLA types are absent, but notably, most people who possess HLA types imparting susceptibility for CD never develop CD. Therefore, while genetic testing in CD can overcome several limitations of the current diagnostic tools, the utility of HLA typing to identify those individuals at increased-risk of CD is limited. Using large datasets assaying single nucleotide polymorphisms (SNPs), we have developed genomic risk scores (GRS) based on multiple SNPs that can more accurately predict CD risk across several populations in “real world” clinical settings. The GRS can generate predictions that optimize CD risk stratification and diagnosis, potentially reducing the number of unnecessary follow-up investigations. The medical and economic impact of improving CD diagnosis is likely to be significant, and our findings support further studies into the role of personalized GRS's for other strongly heritable human diseases.

Quality not quantity for transglutaminase antibody 2: the performance of an endomysial and tissue transglutaminase test in screening coeliac disease remains stable over time

National Institute of Clinical Excellence (NICE) and European Society for Paediatric Gastroenterology, Hepatology and Nutrition (ESPGHAN) guidance for the diagnosis of coeliac disease has been published. However, there is some controversy regarding the advice on the use of stratifying levels of immunoglobulin (IgA) tissue transglutaminase antibody (TG2) test positivity in the absence of test standardization and the vagueness of the indication to test equivocal samples. Using repeat service audit, we demonstrate that a combination of TG2 followed by IgA endomysial antibodies (EMA) is the best strategy for all degrees of mucosal abnormality using our test combination. Reliance upon immunoassay titre is not as effective, and cannot be applied consistently across populations in the absence of assay standardization. Guidelines advocating the use of tests should involve experts in laboratory diagnostics and external quality assurance to ensure that errors of generalization do not occur and that test performance is achievable in routine diagnostic use.

When to reconsider the diagnosis of irritable bowel syndrome

Irritable bowel syndrome (IBS) is a highly prevalent disorder characterized by nonspecific symptoms that can mimic other common medical conditions. A careful history and physical examination may reveal clues that suggest a coexisting or alternative diagnosis, such as small intestinal bacterial overgrowth or celiac disease (CD). Testing for bacterial overgrowth has limitations, but emerging data suggest that antibiotics may be of some benefit in patients with IBS with diarrhea and bloating. CD seems to have a higher prevalence in patients with IBS. Some patients with IBS may have symptomatic improvement on gluten-restricted diets, without histologic or serologic evidence of CD.

Stratifying risk for celiac disease in a large at-risk United States population by using HLA alleles

BACKGROUND & AIMS

Susceptibility to celiac disease (CD) is related to HLA-DQ2 and DQ8 alleles and the heterodimers they encode. The objective of this study was to stratify risk for CD on the basis of HLA-DQ genotype.

METHODS

DNA from 10,191 subjects who are at risk for CD was analyzed for HLA-DQ haplotypes. Individuals with CD were identified as those who tested positive for anti-endomysial immunoglobulin A (EMA+) in an immunofluorescence assay.

RESULTS

Samples homozygous for DQ2.5 (HLA-DQA1 05-DQB1 02) or DQ2.2/DQ2.5 (HLA-DQA1 05-DQB1 02 and HLA-DQA1 0201-DQB1 02) comprised 5.38% of the total; 28.28% of these were EMA+ (95% confidence interval [CI], 24.55-32.26). Of the samples that were DQ2.5 heterozygous (HLA-DQA1 05-DQB1 02); 9.09% were EMA+ (95% CI, 7.82-10.51). Among samples in which HLA-DQ8 (HLA-DQA1 03-DQB1 0302) was detected, 8.42% of homozygotes (95% CI, 3.71-15.92) and 2.11% of heterozygotes (95% CI, 1.43-3.00) were EMA+. Samples with DQ2.2/DQ8 or DQ2.5/DQ8 comprised 5.08% of the total, and 11.78% of these were EMA+ (95% CI, 9.13-14.87). HLA-DQ2 and HLA-DQ8 were absent in 4283 samples (42.03% of the total); 0.16% of these samples were EMA+ (95% CI, 0.07-0.34).

CONCLUSIONS

High-resolution, sequence-specific oligonucleotide probe typing with 35 DQA1-specific and 37 DQB1-specific probes of DNA from more than 10,000 subjects was used to stratify risk of CD in an at-risk U.S. population. DQ2 homozygosity (DQ2.5/DQ2.2+2.5) increased risk for CD, estimated by the rate of EMA positivity, compared with the entire sample population and other DQ genotypes. These data suggest a quantitative relationship between the type/proportion of DQ heterodimers and the risk of CD and identify potential immunotherapeutic targets.

Transglutaminases in inflammation and fibrosis of the gastrointestinal tract and the liver

Transglutaminases are a family of eight currently known calcium-dependent enzymes that catalyze the cross-linking or deamidation of proteins. They are involved in important biological processes such as wound healing, tissue repair, fibrogenesis, apoptosis, inflammation and cell-cycle control. Therefore, they play important roles in the pathomechanisms of autoimmune, inflammatory and degenerative diseases, many of which affect the gastrointestinal system. Transglutaminase 2 is prominent, since it is central to the pathogenesis of celiac disease, and modulates inflammation and fibrosis in inflammatory bowel and chronic liver diseases. This review highlights our present understanding of transglutaminase function in gastrointestinal and liver diseases and therapeutic strategies that target transglutaminase activities.

Etiologies and predictors of diagnosis in nonresponsive celiac disease

BACKGROUND & AIMS

Nonresponsive celiac disease (NRCD) is a common problem affecting from 7% to 30% of celiac patients. Because NRCD comprises varied and potentially morbid entities, efficient and cost-effective patient care requires knowledge of the specific causes of this disorder. The aim of this study was to determine the common etiologies of NRCD in a tertiary referral center.

METHODS

All cases of biopsy examination-proven celiac disease (CD) seen at our institution over the preceding 5 years were included in this study. NRCD was defined as a failure to respond to at least 6 months of treatment with a gluten-free diet or the re-emergence of symptoms or laboratory abnormalities typical of CD while still on treatment with a gluten-free diet.

RESULTS

A total of 113 patients with NRCD meeting the earlier-described criteria were seen from a total of 603 patients with CD (19%), however, among patients for whom we provided primary specialist care the incidence of NRCD was 10% (P < .001). Gluten exposure was the most common cause of NRCD (36%), followed by irritable bowel syndrome (22%), refractory CD (10%), lactose intolerance (8%), and microscopic colitis (6%). The mean immunoglobulin A tissue transglutaminase level in the gluten-exposed group was 67 vs 17 U/mL (normal, <20) for other diagnoses (P < .05). Weight loss and male sex were highly predictive of refractory CD (P < .05 and < .001, respectively).

CONCLUSIONS

NRCD is a common phenomenon affecting 10%-19% of celiac patients. A limited number of etiologies account for the majority of cases. Clinical factors may be used to guide evaluation.

Monitoring non-responsive patients with celiac disease

Current data clearly suggest that VCE has an important role in the diagnostic workup of complicated Cd, especially in those cases with suspected RCd or EATL. This is supported by the high yield of relevant pathological findings in distal parts of the small intestine, such as severe ulceration and mucosal infiltration, by VCE compared to conventional upper GI endoscopy. In this setting, VCE allows for an assessment of the extent of small bowel involvement, detection of overt though often small neoplasms and assists in planning further diagnostic procedures, especially push or double-balloon enteroscopy which are necessary to obtain specimens either to rule out or to confirm aberrant monoclonal T cell proliferation. Currently, those patients in whom RCd type II or EATL are excluded profit most from a thorough diagnostic workup, since most of them can be treated or cured pharmacologically. At present the prognosis of RCd type II or EATL is poor due to lack of effective therapies. However, treatments that effectively target the aberrant lymphocytes can be anticipated.

Diagnostic accuracy of coeliac serological tests: a prospective study

OBJECTIVE

The best way to test serologically for coeliac disease (CD) remains controversial, with endomysial (EMA), transglutaminase (TTG), and gliadin antibodies (AGA) being assessed in various combinations with no apparent standardization. The objective of this study was to evaluate whether TTG-IgA+/-TTG-IgG could be used as a replacement for endomysial antibodies as a reliable screen for CD in patients presenting to a major Australian tertiary referral hospital for assessment of symptoms consistent with CD.

METHODS

Individuals referred for gastroscopic assessment of possible CD were prospectively evaluated by duodenal biopsy assessment. The following diagnostic methods were compared: dual-isotype transglutaminase (TTG-dual), combined-isotype transglutaminase (TTG-IgA+G), TTG-IgA, combined-isotype gliadin antibodies (AGA-IgA+G), AGA-IgA, and endomysial antibody assays. Clinical performance characteristics (sensitivity, specificity, area under the curve for receiver-operating characteristic analysis; AUROC) were assessed for all kits.

RESULTS

The correlation between transglutaminase kits was generally good, with the best transglutaminase kit demonstrating high correlation (r=0.86) with endomysial antibodies. A comparison of different types of endomysial antibody assays displayed variable diagnostic performance (sensitivity 61.90-68.42%; specificity 80.00-98.57%; AUROC 0.71-0.83). Sensitivity (90.48-92.31%), specificity (80.77-82.89%) and AUROC values (0.92-0.94) for dual-isotype transglutaminase kits displayed narrow ranges. AGA assays were less sensitive (AGA-IgA: 42.31-46.15%; AGA-IgG: 61.54%) and less specific (AGA-IgA: 85.09-87.73%; AGA-IgG: 82.46-84.09%). Dual-isotype transglutaminase testing was diagnostically equivalent to transglutaminase-IgA (AUROC 0.92 versus 0.91, P=0.33).

CONCLUSIONS

Our study suggests that transglutaminase screening (using the IgA+/-IgG isotype) is a sensitive and specific alternative to endomysial antibody testing in the serological assessment of CD. On the basis of our findings, AGA antibody testing no longer appears to be an essential part of the diagnostic strategy for adult CD.

Effect of pretreatment of food gluten with prolyl endopeptidase on gluten-induced malabsorption in celiac sprue

BACKGROUND & AIMS

We sought to determine whether prolyl endopeptidase (PEP) treatment of food gluten would obviate the intestinal dysfunction produced by small amounts of dietary gluten supplement in patients with celiac sprue.

METHODS

Twenty asymptomatic patients with histologically proven celiac sprue completed a randomized, double-blind, cross-over study involving two 14-day stages. Each patient consumed a low dose of a gluten supplement daily (5 g; equivalent to 1 slice of bread) in 1 stage and gluten pretreated with PEP in the other stage. Patients completed a daily symptom questionnaire and a D-xylose urine excretion and a 72-hour quantitative fecal fat were monitored before and after each stage.

RESULTS

Despite clinical remission at baseline, 40% of patients had at least 1 abnormal celiac antibody, 20% had an abnormal urine xylose, and 63% had an abnormal fecal fat test result. There was no difference in symptoms as a function of the type of gluten consumed. In response to gluten not treated with PEP, an appreciable proportion of patients developed malabsorption of fat (7 of 17, 41%) or xylose (8 of 14, 57%). When the gluten was pretreated with PEP, fat malabsorption was avoided in 5 of 7 and xylose malabsorption in 4 of 8 of these same patients.

CONCLUSIONS

A significant proportion of asymptomatic patients with celiac sprue have abnormal celiac antibodies and fat or carbohydrate malabsorption. Pretreatment of gluten with PEP avoided the development of fat or carbohydrate malabsorption in the majority of those patients who developed fat or carbohydrate malabsorption after a 2-week gluten challenge.

Pathomechanisms in celiac disease

Celiac disease is an inflammatory disorder of the small intestine caused by an immune response to ingested wheat gluten and similar proteins of rye and barley. It affects at least 1 in 200 individuals, corresponding to roughly three million patients in Western Europe and Northern America alone. Data accumulated since the discovery of gluten specific T cells in the intestine of celiac disease patients the early 1990s have allowed the deciphering of the interplay between the triggering environmental factor, gluten, the main genetic risk factor, the HLA-DQ2/8 haplotypes and the autoantigen; the enzyme tissue transglutaminase (tTG). This established a key role of adaptive immunity orchestrated by lamina propria T cells responding to a set of gluten derived peptides. More recent work points to an important contribution of innate immunity triggered by a distinct gluten peptide and driven by the proinflammatory cytokine Interleukine-5 (IL-15). Together, these observations provide a unique explanation for the disease inducing capacity of gluten.

Clinical features and diagnosis of celiac disease

Celiac disease is a chronic enteropathy caused by intolerance to gluten. The true prevalence of this condition is much greater than previously recognized, with increasing numbers of silent cases being diagnosed. Population-based studies, using serologic screening, have indicated that the prevalence of celiac disease in Caucasian populations is .5%-1%. The pattern of incidence is changing, with a greater proportion of cases diagnosed later in adulthood. The pathologic lesion is characterized by a flattened small intestinal mucosa with a lymphocytic infiltrate, crypt hyperplasia, and villous atrophy. Absorptive function may be impaired and patients can experience gastrointestinal symptoms and malabsorption leading to development of anemia, osteoporosis, or other complications. Untreated celiac disease is associated with significant morbidity and increased mortality, largely owing to the development of enteropathy-associated intestinal lymphoma. The pathologic changes and symptoms resolve when gluten is excluded from the diet for a sustained period.