HLA genotyping is useful in the evaluation of the risk for coeliac disease in the 1st-degree relatives of patients with coeliac disease

Inflammatory auto-immune diseases of the intestine and their management by natural bioactive compounds

Autoimmune diseases are caused by the overactivity of the immune system towards self-constituents. Risk factors of autoimmune diseases are multiple and include genetic, epigenetic, environmental, and psychological. Autoimmune chronic inflammatory bowel diseases, including celiac and inflammatory diseases (Crohn's disease and ulcerative colitis), constitute a significant health problem worldwide. Besides the complexity of the symptoms of these diseases, their treatments have only been palliative. Numerous investigations showed that natural phytochemicals could be promising strategies to fight against these autoimmune diseases. In this respect, plant-derived natural compounds such as flavonoids, phenolic acids, and terpenoids exhibited significant effects against three autoimmune diseases affecting the intestine, particularly bowel diseases. This review focuses on the role of natural compounds obtained from medicinal plants in modulating inflammatory auto-immune diseases of the intestine. It covers the most recent literature related to the effect of these natural compounds in the treatment and prevention of auto-immune diseases of the intestine.

Carrier frequency of HLA-DQB1*02 allele in patients affected with celiac disease: A systematic review assessing the potential rationale of a targeted allelic genotyping as a first-line screening

BACKGROUND

Celiac Disease (CD) is an immune-mediated disorder, in which the HLA immunogenetic background (DQ2 and DQ8 heterodimers) and environmental trigger (gluten) are well established. Indeed, both factors are necessary – but not sufficient – to develop CD. However, it is very likely that CD is underdiagnosed in both developing and developed countries, due to several aspects, including the fact that a lot of patients present mild and/or atypical symptoms, without the presence of any recognized risk factors. Therefore, the possibility and feasibility of widened screening strategies to identify CD patients are debated.

AIM

To provide further evidence of the main epidemiological importance of HLA-DQB1*02 allele in the population of CD patients.

METHODS

We performed a systematic search in PubMed, EMBASE, Cochrane, Web of Science and Scopus databases, in order to produce a systematic review assessing the carrier frequency of HLA-DQB1*02 allele in the celiac population. Following the PRISMA guidelines, we retrieved all the original articles describing CD patients’ HLA-DQB1 genotype in such a way that could allow to assess the HLA-DQB1*02 carrier frequency among CD patients, along with the evidence of the appropriate diagnostic work-up to achieve a correct and final diagnosis of CD.

RESULTS

The final output of this systematic search in the medical literature consisted of 38 studies providing the appropriate HLA-DQB1 genotype information of the respective CD population. According to this systematic review, including a pool of 4945 HLA-DQ genotyped CD patients, the HLA-DQB1*02 carrier frequency was 94.94%, meaning that only 5.06% of CD patients were completely lacking this allelic variant. Interestingly, if we consider only the studies whereby the prevalence of CD patients affected with type 1 diabetes mellitus was supposed or clearly established to be very low, the frequency of non-HLA-DQB1*02 carriers among CD patients dropped to 3.65%.

CONCLUSION

Such a high carrier frequency of the HLA-DQB1*02 allelic variant (which is > 95%-96% in CD patients without risk factors, like type 1 diabetes mellitus comorbidity) might be exploited to consider a cost-effective and widened screening approach. If a sustainable strategy could be implemented through a low-cost targeted genetic test to detect the individual presence of HLA-DQB1*02 allele, an appropriate algorithm for serological screening in individuals resulting to be genetically predisposed to CD, might be considered.

A Clinician's Guide to Celiac Disease HLA Genetics

Celiac disease is a common inflammatory disease triggered by dietary gluten in genetically susceptible individuals. The strongest and best-characterized genetic susceptibilities in celiac disease are class II human leukocyte antigen (HLA) genes known as HLA-DQ2 and DQ8. HLA genetic testing is available through a number of commercial and academic laboratories and is used in the evaluation of celiac disease and to identify at-risk family members. Importantly, HLA genetic testing has a high negative predictive value for celiac disease, but a low positive predictive value. Therefore, for a practicing clinician, it is important to understand when to order HLA genetic testing, what test to order, and how to interpret the result. This review provides a practical primer on HLA genetics in celiac disease.

Relevance of HLA-DQB1*02 Allele in the Genetic Predisposition of Children with Celiac Disease: Additional Cues from a Meta-Analysis

Background and Objectives: Celiac disease (CD) is a multifactorial immune-mediated disorder, triggered by the ingestion of gluten in genetically-predisposed subjects carrying MHC-DQ2 and -DQ8 heterodimers, which are encoded by four HLA-DQ allelic variants, overall. This meta-analysis aims at providing further epidemiological support to the predominant relevance of one specific allele, namely HLA-DQB1*02, in the predisposition and genetic risk of CD. Materials and Methods: We performed a search of MEDLINE/PubMed, Embase, Web of Science, and Scopus, retrieving all publications (case-control study, cross-sectional, and retrospective cohort study) on the association between HLA class II polymorphisms and first-degree relatives (FDRs) of children with CD. After a critical reading of the articles, two investigators independently performed data extraction according to the following inclusion criteria: HLA class II genes, any DQ and DR molecules, and CD diagnosed following the current clinical guidelines. A third participant was consulted for discussion to reach an agreement concerning discrepancies. Results: Our search strategy selected 14 studies as being eligible for inclusion, and those were submitted for data extraction and analysis. These studies were published between 1999 and 2016 and, collectively, enrolled 3063 FDRs. Positive and negative likelihood ratios (LR+ and LR-, respectively) for CD diagnosis, according to the presence of the HLA-DQ genotype coding a complete MHC-DQ2 and/or MHC-DQ8 molecules, were 1.449 (CI 1.279-1.642) and 0.187 (CI 0.096-0.362), respectively. If only the isolated presence of HLA-DQB1*02 allele is considered, the pooled estimation of LR+ was 1.659 (CI 1.302-2.155) and, importantly, the LR- still showed a very good discriminatory power of 0.195 (CI 0.068-0.558). Conclusions: Through our differential meta-analysis, comparing the presence of the genotype coding the full MHC-DQ2 and/or DQ8 molecules with the isolated presence of HLA-DQB1*02 allelic variant, we found that the LR- of the latter analysis maintained the same value. This observation, along with previous evidences, might be useful to consider potential cost-effective widened screening strategies for CD in children.

The potential usefulness of human leukocyte antigen typing for celiac disease screening: A systematic review and meta-analysis

BACKGROUND AND AIM

The presence of specific human leukocyte antigen-DQ2 and DQ8 seems to be necessary for celiac disease development, but the real contribution of its typing for screening is still uncertain. We aim to conduct a systematic review and meta-analysis of the diagnostic performance of human leukocyte antigen typing tests for celiac disease screening.

METHODS

Systematic review of published studies assessing accuracy of human leukocyte antigen DQ2 and DQ8 typing for the detection of celiac disease were selected. MEDLINE and EMBASE were searched from 1st January 2004 until 31st December 2013. Two independent researchers carried out selection and classification of studies, data extraction and analysis. Meta-analysis combining sensitivities, specificities and likelihood ratios of HLA-DQ2 and DQ8 for the diagnosis of celiac disease were carried out.

RESULTS

6 studies including 1303 individuals were finally evaluated. Pooled sensitivity was 98% (95% confidence interval: 97-99). Overall specificity was 45% (95% confidence interval: 41-48). Regarding specificity, studies were heterogeneous and a subgroup analysis was done according to the type of population included. Overall negative likelihood ratio was 0.05 (0.03-0.09).

CONCLUSIONS

Due to its great sensitivity and low negative likelihood ratio, human leukocyte antigen-DQ2/DQ8 typing would be an appropriate test for ruling out celiac disease in the general population suffering related symptoms, and even more in at risk population.

Structural and Functional Changes in the Tight Junctions of Asymptomatic and Serology-negative First-degree Relatives of Patients With Celiac Disease

BACKGROUND

Ten to 15% of first-degree relatives (FDRs) of celiac disease (CeD) patients develop CeD. Although intestinal barrier functions (intestinal permeability) are abnormal in the subset of serology-negative FDRs, what leads to the abnormal barrier function is not known.

GOALS

To study the ultrastructure and functions of tight junctions in serology-negative FDRs of CeD patients.

STUDY

The intestinal permeability was measured in 97 asymptomatic and anti-tissue transglutaminase antibody (anti-tTG Ab)-negative FDRs (using the lactulose mannitol ratio) and in 75 controls. The ultrastructure of tight junctions using transmission electron microscopy, and the expression of key tight junction proteins (claudin-2, claudin-3, occludin, JAM-A, and ZO-1) and zonulin using real-time PCR and immunohistochemistry were assessed in anti-tTG Ab-negative, HLA-DQ2/-DQ8-positive FDRs having normal villi and in disease controls. In addition, the serum zonulin level was measured in 172 anti-tTG Ab-negative FDRs and 198 controls.

RESULTS

The intestinal permeability was significantly increased in FDRs than in controls. Ultrastructural abnormalities such as dilatation of the tight junction (P=0.004) and loss of the pentalaminar structure (P=0.001) were more common in FDRs than in disease controls. There was significant underexpression of tight junction proteins ZO-1 (P=0.040) and occludin (P=0.041) in FDRs. There was no significant difference in the serum zonulin level between FDRs and controls (P=0.154).

CONCLUSIONS

Even asymptomatic, anti-tTG-Ab-negative FDRs with a normal villous histology have both ultrastructural and functional abnormalities in tight junctions. These findings are indirect evidence of the presence of tight junction abnormalities before the onset of the disease and may have therapeutic implications.

Prevalence of celiac disease among first-degree relatives of Indian celiac disease patients

BACKGROUND

Celiac disease, once thought to be uncommon in Asia, is now recognized in Asian nations as well. We investigated the prevalence of celiac disease in first-degree relatives of celiac disease patients followed in our centre.

METHODS

First-degree relatives were screened prospectively for celiac disease using questionnaire-based interview and anti-tissue transglutaminase antibody. Serology positive first-degree relatives underwent duodenal biopsies. Diagnosis of celiac disease was made based on positive serology and villous abnormality Marsh grade 2 or higher. Human leucocyte antigen DQ2/-DQ8 was also assessed in 127 first-degree relatives.

RESULTS

434 first-degree relatives of 176 celiac disease patients were prospectively recruited; 282 were symptomatic (64.9%), 58 were positive for serology (13.3%). Seroprevalence was higher in female than in males (19% vs 8.5%; p=0.001) and highest in siblings (16.9%) than parents (13.6%) and children (5.9%) of celiac patients (p=0.055); 87.4% first-degree relatives were human leucocyte antigen-DQ2/-DQ8 positive. Overall prevalence of celiac disease was 10.9% amongst first-degree relatives.

CONCLUSIONS

The prevalence of celiac disease in first-degree relatives of celiac disease patients was 10.9% in our cohort, and 87% had human leucocyte antigen-DQ2 or -DQ8 haplotype. All first-degree relatives of celiac disease patients should be screen for celiac disease even if asymptomatic or with atypical manifestations.

Appropriate clinical use of human leukocyte antigen typing for coeliac disease: an Australasian perspective

The past decade has seen human leukocyte antigen (HLA) typing emerge as a remarkably popular test for the diagnostic work-up of coeliac disease with high patient acceptance. Although limited in its positive predictive value for coeliac disease, the strong disease association with specific HLA genes imparts exceptional negative predictive value to HLA typing, enabling a negative result to exclude coeliac disease confidently. In response to mounting evidence that the clinical use and interpretation of HLA typing often deviates from best practice, this article outlines an evidence-based approach to guide clinically appropriate use of HLA typing, and establishes a reporting template for pathology providers to improve communication of results.

Clinical utility of celiac disease-associated HLA testing

BACKGROUND

Negative predictive value (NPV) of celiac disease (CD)-related human leukocyte antigens (HLA) DQ2 and DQ8 approaches 100 % in individual patients. However, studies evaluating its exclusionary utility in patient groups are lacking.

AIM

We aim to assess the performance of HLA testing when applied to patient groups with varying characteristics and propose evidence-based recommendations for its clinical use.

METHODS

Demographic and clinical information was recorded in patients undergoing HLA testing. Using predetermined criteria, patients were classified as CD, non-CD, or indeterminate. Diagnostic yield of HLA testing was defined as the percentage of patients in whom CD could be excluded based on negative HLA test.

RESULTS

Two hundred and fifty-six patients underwent testing for CD-related HLA DQ2 and DQ8. 102 (100 non-CD, 2 CD) patients tested HLA negative for a 98 % NPV and 39 % diagnostic yield. Diagnostic yield was highest (60 %) in patients with intraepithelial lymphocytosis plus normal IgA tissue transglutaminase antibody (IgA-tTG) and lowest in patients with positive IgA-tTG plus villous atrophy (0 %). CD was diagnosed in two HLA-negative patients, who carried half of DQ2.5 trans genotype.

CONCLUSIONS

Diagnostic yield of CD-related HLA testing varies widely depending on clinical indication. HLA testing is a practical and valuable test for most patients in whom initial evaluation for CD is inconclusive. A negative HLA result usually obviates the need for further celiac testing including endoscopy and gluten challenge. Rarely, in patients reported as HLA negative, half of HLA DQ2.5 (cis or trans) is sufficient for development of CD.

Late diagnosis of celiac disease in an asymptomatic infant with growth failure

The clinical spectrum for celiac disease (CD) is broad and includes cases with either typical (intestinal) or atypical (extraintestinal) features, often making the diagnosis of CD very difficult.

We describe the case of a girl presenting with stunted growth and malnourishment. She was evaluated at 14 months for decreased growth rate without any signs of gastrointestinal, renal or endocrine disorders. She was evaluated for CD, but resulted negative for anti-tTG antibodies.

At the age of 4.1 years, she exhibited basal dental enamel hypoplasia, iron deficiency anaemia despite repeated iron supplementation, with persistent reduced height (-2.79 SDS), BMI (-0.76 SDS), growth velocity (-1.79 SDS) and delayed bone age (1.5 year). The CD screening was repeated and very high anti-tTG-IgA (128 IU/ml, normal values < 7 IU/ml) and anti-tTG-IgG (77 IU/ml, normal values < 7 IU/ml) values were found. HLA genotyping revealed an HLA DQ2 haplotype. A duodenal biopsy revealed severe villous atrophy with crypt hyperplasia and increased intraepithelial lymphocytes (> 40 IELs/100 epithelial cells) confirming the diagnosis of CD. A gluten-free diet was started and after only four months, her growth velocity increased from 4.83 cm/year (-1.79 SDS) to 6.53 cm/year (-0.15 SDS).

In conclusion, we report the development of a positive serology for CD in an asymptomatic child with growth retardation, who previously was investigated for CD and resulted negative. Therefore, when faced with retarded growth in young patients, after excluding other malabsorption conditions and even when CD serological markers are negative, the paediatric endocrinologist should request HLA genotyping, before the intestinal biopsy, in order to check for the presence of risk alleles.

HLA DR-DQ genotyping by capillary electrophoresis for risk assessment for celiac disease

The risk for celiac disease (CD) is clearly related to specific HLA DQA1 and DQB1 alleles, but HLA -typing is often considered too costly for frequent use.Here we present a method using sequence-specific primed PCR (PCR-SSP) for HLA-DR-DQ genotyping optimized for capillary electrophoresis on Applied Biosystems 3130xl Genetic Analyzer. Requiring a total of three PCR reactions and a single electrophoretic step, this method reduces the reagent expenses and technical time for directed HLA typing to distinguish risk alleles for CD, with a sufficient throughput for large-scale screening projects.

Serologic screening and genetic testing among brazilian patients with celiac disease and their first degree relatives

CONTEXT

Celiac disease susceptibility has been shown to be associated with the HLA alleles DQA1*0501 and DQB1*0201 (together encoding the DQ2 heterodimer) that are present in practically all celiac disease patients. The DQ8 heterodimer (coded by DQA1*03-DQB1*0302), which is carried on a DRB1*04 (DR4) haplotype, is commonly encoded for by the few celiacs who do not carry the DQ2 heterodimer. Only a few celiac disease patients have been reported without these known risk alleles.

OBJECTIVE

To assess the prevalence of celiac disease in a group of first degree relatives of celiac patients, and the frequency of HLA predisposing alleles both in the group of celiac patients and in their first degree relatives, identifying those first degree relatives who would need further screening for celiac disease.

METHODS

Ninety celiac disease patients and 207 first degree relatives underwent serologic screening for celiac disease (endomysial and transglutaminase antibodies) followed by intestinal biopsy in positive patients. The HLA-DQA1*0501, DQB1*0201 and DRB1*04 frequencies of celiac patients and their first degree relatives were determined utilizing the PCR method.

RESULTS

All the celiac disease patients (n = 90) with the exception of one (1.1%) carried at least one of the alleles investigated. Altogether 11 (5.3%) of the investigated first degree relatives did not carry any of the alleles studied. Fourteen (6.7%) new cases of celiac disease were found among the 207 celiac disease patients first degree relatives.

CONCLUSIONS

Considering the cost-benefit of the HLA typing of all the first degree relatives of celiac patients, their HLA status should be decided on an individual basis, taking account of their profile and preferences, and the existence of other medical conditions.

HLA-DQ genotyping combined with serological markers for the diagnosis of celiac disease: is intestinal biopsy still mandatory?

OBJECTIVES

The aim of this study was to evaluate the value of HLA-DQ2/DQ8 allelic genotyping combined with serologic testing for the diagnosis of celiac disease (CD).

PATIENTS AND METHODS

One hundred seventy children, who underwent jejunal biopsy for digestive symptoms or malnutrition, were tested for HLA-DQ2/DQ8 and serologic markers (tTG and/or anti-endomysial antibodies). Children were classified in 2 groups, according to jejunal histology: group 1, when partial or total villous atrophy was associated with an increased intraepithelial lymphocytosis suggesting CD, and group 2, when these histological criteria were absent.

RESULTS

Eight children were excluded from the study because their intestinal histology was not informative; 82 children were classified in group 1 and 80 in group 2. Eighty-one of 82 children in group 1 were positive for HLA and serologic testing. The other child had negative HLA and serologic testing but marked villous atrophy, and further investigation showed an allergic disease. Among the 80 children in group 2, 53 were negative for both HLA and serologic testing, 22 were positive for HLA but negative for serologic testing, 2 were negative for HLA and positive for serologic testing, and 3 patients were positive for both HLA and serologic testing. The last 3 children were shown to have an autoimmune background and had probably a latent form of CD. The association of HLA-DQ2/DQ8 and serologic markers had a sensitivity of 98.8%, a specificity of 96.2%, a positive likelihood ratio of 26.3, and a negative likelihood ratio of 0.013.

CONCLUSIONS

The association of positive HLA-DQ2/DQ8 and serologic testing has a high predictive value for CD. We suggest that symptomatic children with high titers of immunoglobulin (Ig)A tTG could be diagnosed as patients with CD without performing jejunal biopsy. In other children, HLA-DQ2/DQ8 could be useful to exclude the diagnosis of CD if negative. In cases of low IgA tTG titers or in patients with IgA deficiency, intestinal biopsy remains mandatory.

A new PCR-SSP method for HLA DR-DQ risk assessment for celiac disease

BACKGROUND

Susceptibility to celiac disease is essentially restricted to carriers of specific HLA DQA1 and DQB1 alleles. We have developed a semi-automated sequence specific primer (SSP) PCR method for clinical HLA typing and compared the test results with those from a commercial method.

METHODS

Primers for each DQA1 and DQB1 allele group were included in our PCR-SSP reaction to allow differentiation of homozygous from heterozygous carriers of risk alleles. Primers detecting the tightly linked DRB1*04, *03, *07 and *09 alleles were included to resolve potentially ambiguous results. Fluorescently labeled PCR products of 119 clinical samples were analyzed by capillary electrophoresis, and results were compared to those previously obtained from the DELFIA® Type 1 Diabetes Genetic Predisposition assay.

RESULTS

The risk assessment derived from the two methods was 100% concordant. One previously unreported haplotype was detected and haplotype assignments in two of the 119 samples were improved from previous reports.

CONCLUSIONS

The use of three PCR reactions and a single electrophoretic step for DQA1, DQB1 and DRB1 typing provides distinction of celiac disease associated alleles and their homo- or heterozygous status. This multiplex analysis reduces reagent costs, personnel and instrument time, while enabling improved allelic assignment through HLA-DR-DQ haplotype association.

Association of Doberman hepatitis to canine major histocompatibility complex II

Doberman hepatitis (DH) is a chronic and progressive inflammatory liver disease that mainly affects female dogs. The high incidence of chronic hepatitis in Dobermans is suggestive of a genetic predisposition. DH is characterized by mononuclear cell infiltration and copper accumulation in the liver and major histocompatibility complex (MHC) class II antigen expression in the hepatocytes. In dogs, the MHC is referred to as the dog leukocyte antigen (DLA) system. In this study, the potential role of DLA genes in DH was investigated by sequence-based typing in the exon 2 of DLA-DRB1, -DQA1 and -DQB1. The case group comprised 37 Dobermans with subclinical or clinical DH. The control group consisted of 37 healthy Dobermans, with normal liver enzyme values and without immunosuppressive medication. The control dogs were over 10 years old to include dogs with the lowest genetic risk of DH. Our results indicate that Dobermans with homozygous DLA-DRB1*00601/DQA1*00401/DQB1*01303 [odds ratio (OR) = 14.9, confidence limit (CL) = 3.1-71.7, P < 0.00005], especially with homozygosity for DLA-DRB1*00601 (P < 0.0005), are susceptible to DH. The DQ heterodimer DLA-DQA1*00901/DQB1*00101 and the allele DLA-DRB1*01501 appear to confer protection against DH (P < 0.001). Allele and haplotype frequencies were compared using chi-squared statistics. The disease shows a complex pattern of inheritance, but the observed DLA class II association with DH suggests a role for the immune system in the development of the disease.

Risk factors in familial forms of celiac disease

Celiac disease has been reported in up to 2% of some European populations. A similar risk has been identified in the America and Australia where immigration of Europeans has occurred. Moreover, an increasing number of celiac disease patients are being identified in many Asian countries, including China and India. Finally, celiac disease has also been detected in Asian immigrants and their descendants to other countries, such as Canada. Within these so-called "general" celiac populations, however, there are specific high risk groups that have an even higher prevalence of celiac disease. Indeed, the single most important risk factor for celiac disease is having a first-degree relative with already-defined celiac disease, particularly a sibling. A rate up to 20% or more has been noted. Risk is even greater if a specific family has 2 siblings affected, particularly if a male carries the human leukocyte antigen-DQ2. Both structural changes in the small bowel architecture occur along with functional changes in permeability, even in asymptomatic first-degree relatives. Even if celiac disease is not evident, the risk of other autoimmune disorders seems significantly increased in first-degree relatives as well as intestinal lymphoma. Identification of celiac disease is important since recent long-term studies have shown that the mortality of celiac disease is increased, if it is unrecognized and untreated.

The spectrum of celiac disease: epidemiology, clinical aspects and treatment

Celiac disease is a gluten-sensitive enteropathy that affects people of all ages worldwide. This disease has emerged as a major health-care problem, as advances in diagnostic and screening methods have revealed its global prevalence. Environmental factors such as gluten introduction at childhood, infectious agents and socioeconomic features, as well as the presence of HLA-DQ2 and/or HLA-DQ8 haplotypes or genetic variations in several non-HLA genes contribute to the development of celiac disease. Growing insight into the variable clinical and histopathological presentation features of this disease has opened new perspectives for future research. A strict life-long gluten-free diet is the only safe and efficient available treatment, yet it results in a social burden. Alternative treatment modalities focus on modification of dietary components, enzymatic degradation of gluten, inhibition of intestinal permeability and modulation of the immune response. A small group of patients with celiac disease (2-5%), however, fail to improve clinically and histologically upon elimination of dietary gluten. This complication is referred to as refractory celiac disease, and imposes a serious risk of developing a virtually lethal enteropathy-associated T-cell lymphoma.

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.

Genetic testing before serologic screening in relatives of patients with celiac disease as a cost containment method

GOALS AND BACKGROUND

Relatives of patients with celiac disease have an increased lifetime risk of developing celiac disease. Repeat screening of relatives would improve diagnosis rates, but at significant cost. Genetic testing before screening would potentially reduce costs by eliminating HLA-DQ2 and DQ8 negative patients who are at extremely low risk for developing celiac disease.

STUDY

A decision tree was developed incorporating 3 diagnostic branches: initial screening with anti-tissue transglutaminase at time t0, repeat screening at time t1, and genetic testing before repeat screening. Costs were estimated using Medicare reimbursement fees. Modeling and sensitivity analyses were performed using Tree Age Pro 2006.

RESULTS

The cost of an initial screening with anti-tissue transglutaminase is approximately $434 per person. Repeat screening would cost $683, but would diagnosis an additional 4.4% cases. Genetic testing before screening would cost $750, but would decrease the lower endoscopy workload by nearly 25%. Genetic testing would have to decrease from $301 to $234, a difference of $67, to justify its use before serologic testing. As the specificity of anti-tissue transglutaminase approaches 100%, the cost of genetic testing would have to continue to decrease to less than $200 in order for it to be an affordable option.

CONCLUSIONS

Repeat screening of relatives with celiac disease results in a significant increase in cost, but also an associated increase in cases diagnosed. Genetic testing would potentially eliminate up to 60% of the population to be screened and, if available at a lower cost, would partially offset costs of repeat serologic screening.

HLA and autoimmune digestive disease: a clinically oriented review for gastroenterologists

OBJECTIVES

The human leukocyte antigen (HLA) system includes genes involved in graft-vs-host rejection and in immune response. The discovery that HLAs are associated with several diseases led to appealing developments both in basic biomedical research and in clinical medicine, and offered the opportunity to improve the understanding of pathogenesis and classification of diseases, as well as to provide diagnostic and prognostic indicators. The aim of this article is to review the association between HLA alleles and autoimmune digestive disease and its current relationship with modern HLA nomenclature and clinical practice.

METHODS

Articles dealing with the association between HLAs and autoimmune digestive disease (including celiac disease, inflammatory bowel disease, autoimmune hepatitis, sclerosing cholangitis and primary biliary cirrhosis) were searched for using Pubmed and SCOPUS databases from earliest records to January 2008.

RESULTS

The review has provided two sections. In the first, we explain the basic principles of HLA structure, function, and nomenclature, as an introduction to the second section, which describes current associations between HLA alleles and digestive diseases. The clinical implications of each HLA association are critically discussed. Actually, a clinical role for HLA typing is suggested for only a few conditions, e.g., celiac disease.

CONCLUSIONS

The knowledge of current HLA nomenclature and of its association with some digestive diseases such as celiac disease can be useful in clinical practice for diagnostic and prognostic purposes. This can avoid improper HLA typing as well as stressing the need for further studies on other possible clinical applications.

Predictors of family risk for celiac disease: a population-based study

BACKGROUND & AIMS

There is an elevated prevalence of celiac disease (CD) in family members (FMs) of CD patients, but most prior studies have been done on selected populations. Our aim was to determine the clinical, serologic, and genetic predictors of CD in FMs of a population-based cohort of index cases.

METHODS

Index cases from southeast Minnesota provided contact information for their first-degree relatives. FMs were examined for endomysial antibodies (EMAs), tissue transglutaminase antibodies (tTGAs), and HLA-DQ genotyping. Two questionnaires were applied, Bowel Disease Questionnaire and Short Form Health Survey. Intestinal biopsies were offered if there were any positive autoantibody or seronegative FMs with gastrointestinal symptoms and HLA-DQ at risk for CD.

RESULTS

We recruited 111 index cases that had 579 FMs, of whom 344 (59%) were investigated. The average screening rate among families was 65%. A positive tTGA test was found in 47 (14%), 33 with a positive EMA test. CD was diagnosed in 39 (21 males), with an estimated prevalence of 11% (lambda(R) = 16.1). All affected FMs carried the at-risk genotypes. Twenty-one (54%) had "silent" disease, most with severe intestinal villous atrophy. Carrying HLA-DQ2 (odds ratio, 16.1; 95% confidence interval, 2.1-123) and being a sibling (odds ratio, 2.5; 95% confidence interval, 1.1-5.8) are high-risk factors for CD.

CONCLUSIONS

CD is more common in first-degree relatives than previously reported in the United States, with siblings having the greatest risk. There is male preponderance of new cases, and many had silent disease despite severe histologic injury. A more proactive case-finding strategy in FMs might improve the diagnostic rate of CD in North America.

Human leucocyte antigen and TNFalpha polymorphism association in microscopic colitis

OBJECTIVES

Coeliac disease (CD) is common in patients with microscopic colitis (MC). The human leucocyte antigen (HLA)-DR3-DQ2 haplotype is strongly associated with CD, and there is evidence for an association with MC. We analysed the genetic background of MC by assessing the haplotypes of HLA-DR3-DQ2 and HLA-DR4-DQ8. In addition, TNFalpha gene polymorphism (-308) associated with susceptibility to several autoimmune diseases was studied.

METHODS

Eighty patients with MC including 29 with collagenous colitis (CC) and 51 with lymphocytic colitis (LC) were typed for HLA-DR3-DQ2, and HLA-DR4-DQ8 molecule encoding genes using either an allele-specific PCR, or hybridization with sequence-specific oligonucleotides. Duodenal biopsies (N=78) confirmed the diagnosis of CD in 15 (18.8%) patients. TNFalpha(308) alleles were analyzed in 78 patients with MC (27 with CC and 51 with LC). A control group of 3627 patients was used in the HLA study and 178 patients in the TNFalpha study.

RESULTS

HLA-DR3-DQ2 haplotype was more frequent in patients with MC (43.8%) including both subgroups (LC, 44.8%; CC, 43.1%; P<0.001), and MC with CD (86.7%; P<0.001) and without CD (33.3%; P=0.003), compared with the controls (18.1%). Similarly, the TNF2 carrier rate was higher in MC (46.2%; P<0.001) including both CC (44.4%; P=0.031) and LC (47.1%; P=0.001), and both MC patients with CD (66.7%; P=0.001) and without CD (39.3%; P=0.019), compared with the controls (23%).

CONCLUSION

Both CC and LC are associated with the HLA-DR3-DQ2 haplotype and with TNF2 allele carriage. These associations are present also in MC patients without CD. The shared predisposing HLA-DR3-DQ2 haplotype and the high prevalence of CD in patients with MC suggest an epidemiological overlap, and probably some similarities in the pathogenesis of CD and MC.