Inter- and Intra-assay Variation in the Diagnostic Performance of Assays for Anti-tissue Transglutaminase in 2 Populations

The role of serology in the diagnosis of coeliac disease

Serology has significantly revolutionized the knowledge of celiac disease (CD), leading to the identification of unsuspected patients in at-risk CD groups, thereby increasing the number of CD diagnoses compared to the pre-screening era. Several markers for CD with a progressive diagnostic accuracy have been identified over the years, but only three of them, i.e. anti-tissue transglutaminase (anti-tTG), anti-endomysial (EmA) and anti-deamidated gliadin antibodies (DGP) are currently assessed in the daily clinical practice. A thorough review of the literature identified 44 original studies published between 1998 to 2022 for a total of 5098 pediatric and adult CD patients (without selective IgA deficiency) and 11930 disease controls. The results highlighted that anti-tTG IgA exhibited a higher sensitivity for CD (93.4%) than EmA IgA (92.8%), DGP IgG (81.8%) and DGP IgA (83.8%). The specificity of EmA IgA (99%) resulted to be higher than those of anti-tTG IgA (95.8%), DGP IgG (96.4%) and DGP IgA (92.1%). In patients with selective IgA deficiency, a condition closely related to CD, serological screening should include one of the three antibodies of IgG class, since anti-tTG, DGP and EmA have a very similar diagnostic accuracy in this clinical setting. According to age, there are two main diagnostic strategies for CD detection. In children, the revised ESPGHAN 2020 guidelines established that CD could be diagnosed in both symptomatic and asymptomatic children by high anti-tTG IgA titers (>10 times the cut-off) and EmA positivity with no need to obtain duodenal biopsy and HLA typing. In adult patients, although high tTG IgA titers (confirmed by EmA IgA positivity) correlate with villous atrophy, an intestinal biopsy is still considered mandatory for confirming CD diagnosis. Currently, a case finding approach in at-risk groups is preferred to mass screening for CD detection.

Prevalence of celiac disease in patients with liver diseases: a systematic review and meta-analyses

OBJECTIVES

A subset of patients with celiac disease (CeD) have liver involvement in the form of hypertransaminasemia, liver cirrhosis and autoimmune hepatitis. We conducted a systematic review with meta-analyses to determine pooled prevalence of CeD in patients with cryptogenic cirrhosis, all-cause cirrhosis, cryptogenic hypertransaminasemia, and all-cause hypertransaminasemia.

METHODS

We searched PubMed and EMBASE up to January 2022. Cross-sectional, case-control and prospective cohort studies performing serological tests and/or intestinal biopsy for CeD on patients with cryptogenic cirrhosis, all-cause cirrhosis, cryptogenic hypertransaminasemia and all-cause hypertransaminasemia were included, to calculate pooled estimates of seroprevalence and prevalence of biopsy-confirmed CeD in these four groups.

RESULTS

Of 6,871 articles screened, 20 articles were included finally in three meta-analyses for cryptogenic cirrhosis, all-cause cirrhosis and cryptogenic hypertransaminasemia. For the all-cause hypertransaminasemia group, a qualitative review of four studies was done instead of a meta-analysis, due to significant differences in studies. The pooled prevalence (95%CI) of biopsy-confirmed CeD, in cryptogenic cirrhosis was 4.6%(2.2-7.5%) while pooled prevalence of biopsy-confirmed CeD in all-cause cirrhosis was 0.8%(0-3.4%). Pooled prevalence of biopsy-confirmed CeD in cryptogenic hypertransaminasemia was 5.7%(3.2-8.8%).

CONCLUSIONS

Nearly one in 20 patients each with cryptogenic cirrhosis and cryptogenic hypertransaminasemia have CeD, hence they should both be considered high-risk groups for CeD. While prevalence of CeD in all-cause cirrhosis is similar to that in general population, it may be worth screening them for CeD as liver pathology has potential for reversal in them.

Who to screen and how to screen for celiac disease

Celiac disease (CeD) is a chronic gluten-induced enteropathy with plethoric manifestations. The typical manifestations of CeD such as chronic diarrhea and malabsorption are widely recognized, however, many patients have atypical manifestations like iron deficiency anemia, idiopathic short stature, hypertransaminesemia or infertility, etc. These patients often present to the primary care physicians and/or non-gastrointestinal specialties. However, due to a lack of awareness among the healthcare professionals about the various atypical manifestations, many patients are not screened for CeD. In this review, we have summarized the available literature about the prevalence of CeD in various gastrointestinal (chronic diarrhea) and non-gastrointestinal conditions (iron deficiency anemia, short stature, cryptogenic hypertransaminesemia, cryptogenic cirrhosis or idiopathic ataxia etc.) where the diagnosis of CeD should be con-sidered. In addition, we also discuss special scenarios where screening for CeD should be considered even in absence of symptoms such as patients with type 1 diabetes, Down’s syndrome, and first-degree relatives of patients with CeD. Further, we discuss the diagnostic performance and limitations of various screening tests for CeD such as IgA anti-tissue transglutaminase antibodies, anti-endomysial antibodies and anti-deamidated gliadin antibodies. Based on the current recommendations, we propose a diagnostic algorithm for patients with suspected CeD.

The Prevalence of the Celiac Disease in Patients with Dyspepsia: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with celiac disease (CeD) can commonly present with symptoms of dyspepsia. We conducted a systematic review and meta-analysis of the present literature to assess the prevalence of CeD in patients diagnosed with dyspepsia.

METHODS

We searched MEDLINE and EMBASE databases for the keywords: celiac disease, coeliac disease, anti-gliadin, tissue transglutaminase antibody, anti-endomysial antibody, dyspepsia and functional gastrointestinal disorder. All the studies published from January 1991 till May 2021 were included. Diagnosis of CeD was based on the European Society of Pediatric Gastroenterology, Hepatology and Nutrition guidelines. A random-effects model was used to pool the data.

RESULTS

Twenty-one studies screening 10,275 patients with dyspepsia were included. The pooled seroprevalence of CeD based on a positive anti-tissue transglutaminase antibody and/or anti-endomysial antibody was 4.8% (95% CI [2.8, 6.7%], I² = 87.7%). The pooled biopsy-confirmed CeD prevalence was 1.5% (95% CI [1.0, 1.9%]; I² = 59.8%) in these patients. Both seroprevalence (Odds ratio: 1.8; 95% CI [0.8, 4.0%]; I² = 0%) and prevalence of biopsy-confirmed CeD (Odds ratio: 1.4; 95% CI [0.8, 2.4]; I² = 0%) were not higher in patients with dyspepsia compared to controls. There was a moderate risk of selection bias and significant heterogeneity in the pooled results.

CONCLUSIONS

The pooled prevalence of CeD in patients with dyspepsia was 1.5% and it was not significantly higher than the general population. These results do not support screening of patients with dyspepsia for CeD.

The global burden of coeliac disease: opportunities and challenges

Coeliac disease is a systemic disorder characterized by immune-mediated enteropathy, which is caused by gluten ingestion in genetically susceptible individuals. The clinical presentation of coeliac disease is highly variable and ranges from malabsorption through solely extra-intestinal manifestations to asymptomatic. As a result, the majority of patients with coeliac disease remain undiagnosed, misdiagnosed or experience a substantial delay in diagnosis. Coeliac disease is diagnosed by a combination of serological findings of disease-related antibodies and histological evidence of villous abnormalities in duodenal biopsy samples. However, variability in histological grading and in the diagnostic performance of some commercially available serological tests remains unacceptably high and confirmatory assays are not readily available in many parts of the world. Currently, the only effective treatment for coeliac disease is a lifelong, strict, gluten-free diet. However, many barriers impede patients' adherence to this diet, including lack of widespread availability, high cost, cross-contamination and its overall restrictive nature. Routine follow-up is necessary to ensure adherence to a gluten-free diet but considerable variation is evident in follow-up protocols and the optimal disease management strategy is not clear. However, these challenges in the diagnosis and management of coeliac disease suggest opportunities for future research.

Emergence of Celiac disease and Gluten-related disorders in Asia

Celiac disease (CeD) is a systemic, immune-mediated enteropathy, which is triggered by gluten protein in genetically susceptible individuals. CeD, once thought to be an uncommon disease, is now recognized to affect approximately 40-60 million people globally. While CeD is now well reported from a few Asian countries such as India, China, Pakistan, and Middle Eastern countries; it is still believed to be uncommon in the rest of Asia. Gluten-related diseases other than CeD, like non-celiac gluten sensitivity (NCGS) are also emerging globally. CeD and NCGS may present with either intestinal or extra-intestinal symptoms, and a proportion of them have overlapping symptoms with irritable bowel syndrome. Hence, many of them are misdiagnosed as having irritable bowel syndrome in clinical practice. In this review, we discuss the emergence of CeD and other gluten-related disorders, both globally and in Asia, the overlapping manifestations between gluten-related disorders and irritable bowel syndrome, and the challenges associated with diagnosis and management of CeD in Asia.

Opportunities and challenges in the management of celiac disease in Asia

Although once considered uncommon, there is increasing recognition of celiac disease (CeD) in Asia. It is now clear that CeD is a disorder as frequent in certain Asian countries as that in western countries, although it often remains undiagnosed. With increasing awareness and diagnosis, the absolute numbers of celiac patients are expected to increase markedly in Asia. Asia, with 60% of the population of the world, is probably the major "reservoir" of undiagnosed CeD in the world. As Asia has a huge landscape along with highly heterogenous genetic, social, cultural, and nutritional practices, similar heterogeneity is seen in the epidemiology, diagnostic, and therapeutic facilities for CeD in Asia. In this article, we have reviewed the changes in the epidemiology, diagnostics, and management of CeD in Asia and summarized the challenges and opportunities for its emergence in Asia.