Estimating the Impact of Verification Bias on Celiac Disease Testing

Laboratory Testing for Celiac Disease: Clinical and Methodological Considerations

BACKGROUND

Celiac disease (CeD) has an estimated prevalence of 1%-3%. The classical clinical presentation is malabsorption, but now patients may present with more subtle symptoms such as constipation, osteoporosis, or iron deficiency anemia. Children may also present with poor growth.CeD has a strong genetic component, and high-risk groups include first-degree relatives with CeD, patients with co-existing autoimmune diseases, and patients with chromosomal aberrations.

CONTENT

Diagnostic tests for CeD include duodenal histology, serology, and genetic testing. Duodenal histology has traditionally been the gold standard of diagnosis. However, serological tests, especially IgA tissue transglutaminase antibodies (TTG-IgA), are widely used and diagnostic algorithms are based primarily on TTG-IgA as a starting point. Human leukocyte antigen typing may also be incorporated to determine genetic risk for CeD. Guidelines for children endorse biopsy avoidance provided high levels of TTG-IgA, with diagnostic accuracy being comparable to duodenal biopsy. Confirmation may be achieved by identifying IgA endomysial antibodies in a separate blood sample. Subjects with low positive TTG-IgA levels and subjects with IgA deficiency need a biopsy to establish a diagnosis of CeD. The clinical follow-up of CeD usually includes a repeat TTG-IgA examination. In adults, healing may be delayed or incomplete, and a rare consequence of refractory celiac disease is transformation to enteric T-cell lymphoma.

SUMMARY

Laboratory testing, in particular TTG-IgA, plays a central role in the diagnosis and has an accuracy comparable to histology. Diagnostic algorithms utilizing laboratory testing are critical for the development of novel strategies to improve diagnosis.

Clinical Features of Children With Serology Negative, Biopsy Positive Celiac Disease

The prevalence of pediatric serological negative celiac disease (SNCD) is poorly described, with few recognized clinical predictors beyond immunoglobulin A (IgA) deficiency or reduced gluten intake. The purpose of this retrospective review was to describe the prevalence of SNCD at the Stollery Children's Hospital and identify clinical features to help in recognition of these cases. Patients with a positive biopsy and negative serology (SNCD) were compared to those with positive biopsy and serology. SNCD diagnosis required clinical correlation and either confirmatory genetics or follow up endoscopy on a gluten-free diet. Of the 424 patients who met celiac disease (CD) criteria, 4.7% (n = 20) fulfilled our criteria for SNCD. There was a significant difference in the rates of IgA deficiency between the 2 groups, but no other clinical features were found that allowed for ready identification of SNCD patients.

American College of Gastroenterology Guidelines Update: Diagnosis and Management of Celiac Disease

This guideline presents an update to the 2013 American College of Gastroenterology Guideline on the Diagnosis and Management of Celiac Disease with updated recommendations for the evaluation and management of patients with celiac disease (CD). CD is defined as a permanent immune-mediated response to gluten present in wheat, barley, and rye. CD has a wide spectrum of clinical manifestations that resemble a multisystemic disorder rather than an isolated intestinal disease, and is characterized by small bowel injury and the presence of specific antibodies. Detection of CD-specific antibodies (e.g., tissue transglutaminase) in the serum is very helpful for the initial screening of patients with suspicion of CD. Intestinal biopsy is required in most patients to confirm the diagnosis. A nonbiopsy strategy for the diagnosis of CD in selected children is suggested and discussed in detail. Current treatment for CD requires strict adherence to a gluten-free diet (GFD) and lifelong medical follow-up. Most patients have excellent clinical response to a GFD. Nonresponsive CD is defined by persistent or recurrent symptoms despite being on a GFD. These patients require a systematic workup to rule out specific conditions that may cause persistent or recurrent symptoms, especially unintentional gluten contamination. Refractory CD is a rare cause of nonresponsive CD often associated with poor prognosis.

Review article: Diagnosis of coeliac disease: a perspective on current and future approaches

Diagnostics will play a central role in addressing the ongoing dramatic rise in global prevalence of coeliac disease, and in deploying new non-dietary therapeutics. Clearer understanding of the immunopathogenesis of coeliac disease and the utility of serology has led to partial acceptance of non-biopsy diagnosis in selected cases. Non-biopsy diagnosis may expand further because research methods for measuring gluten-specific CD4+ T cells and the acute recall response to gluten ingestion in patients is now relatively straightforward. This perspective on diagnosis in the context of the immunopathogenesis of coeliac disease sets out to highlight current consensus, limitations of current practices, gluten food challenge for diagnosis and the potential for diagnostics that measure the underlying cause for coeliac disease, gluten-specific immunity.

To DGP-IgG or not? A comparison of TTG-IgA and DGP-IgG

BACKGROUND

We assessed the diagnostic utility of deamidated gliadin peptide immunoglobulin G (DGP-IgG) in pediatric patients without immunoglobulin A deficiency who underwent tissue transglutaminase immunoglobulin A (TTG-IgA) screening and biopsy.

METHODS

Patients who had TTG-IgA performed in our laboratory had sample frozen over a 1.5 y. If a patient underwent biopsy within 6 months of serology, DGP-IgG was performed on frozen sample. All testing was performed on the BioPlex 2200. Biopsies were assigned a modified Marsh-Oberhuber score. The sensitivity, specificity, and positive and negative predictive values were calculated for TTG-IgA and DGP-IgG for values ≥ 15 u/ml, 15-149 u/ml, and > 150 u/ml using biopsy as gold standard.

RESULTS

A total of 458 patients were included. Sensitivity and specificity for DGP-IgG ≥ 15 u/ml and Marsh ≥ 2 was 76% and 87.5% and TTG-IgA ≥ 15 was notably higher at 93.3% and 92.2%. Sensitivity and specificity of DGP-IgG were 66% and 88.9% at moderate and 29.3% and 98.4% at high increases. The positive predictive value of DGP-IgG for celiac disease in TTG-IgA negative patients was 2.8%.

CONCLUSIONS

Our study suggests DGP-IgG does not add significant value in patients screened for celiac disease.

Review on pediatric coeliac disease from a clinical perspective

Coeliac disease is an immune-mediated condition characterized by chronic inflammation of the small bowel with villous atrophy driven by gluten ingestion in genetically predisposed individuals. It occurs frequently in both children and adults, affecting 1-4% of the population. The disease is associated with both gastrointestinal and extra-intestinal symptoms related to malabsorption and/or immune activation, and autoantibodies to tissue transglutaminase. Removal of gluten from the diet results in resolution of symptoms and enteropathy in the majority of patients. A good diagnostic work-up is important to avoid unnecessary restrictive diets in children. In this review on pediatric coeliac disease, we address epidemiology including predisposing environmental factors and possible preventive strategies, as well as the clinical presentation, diagnosis and follow-up. What is Known: •Primary prevention of coeliac disease is not possible; however, secondary prevention by targeting high-risk groups is recommended. •The diagnosis is safe without duodenal biopsies if specific conditions are met, also in asymptomatic children. What is New: •HLA-DQ typing is not routinely required for the diagnosis, whereas it can rule out coeliac disease if HLA-DQ2 and HLA-DQ8 are absent. •Follow-up could be improved by a more rational use of (laboratory) tests, increased intention to dietary compliance and quality of life.

Systematic review with meta-analysis: the accuracy of serological tests to support the diagnosis of coeliac disease

BACKGROUND

There is growing support for a biopsy avoidant approach to diagnose coeliac disease in both children and adults, using a serological diagnosis instead.

AIMS

To assess the diagnostic accuracy of serological tests for coeliac disease in adults and children.

METHODS

Seven electronic databases were searched between January 1990 and August 2020. Eligible diagnostic studies evaluated the accuracy of serological tests for coeliac disease against duodenal biopsy. Risk of bias assessment was performed using QUADAS-2. Bivariate random-effects meta-analyses were used to estimate serology sensitivity and specificity at the most commonly reported thresholds.

RESULTS

113 studies (n = 28,338) were included, all in secondary care populations. A subset of studies were included in meta-analyses due to variations in diagnostic thresholds. Summary sensitivity and specificity of immunoglobulin A (IgA) anti-tissue transglutaminase were 90.7% (95% confidence interval: 87.3%, 93.2%) and 87.4% (84.4%, 90.0%) in adults (5 studies) and 97.7% (91.0%, 99.4%) and 70.2% (39.3%, 89.6%) in children (6 studies); and of IgA endomysial antibodies were 88.0% (75.2%, 94.7%) and 99.6% (92.3%, 100%) in adults (5 studies) and 94.5% (88.9%, 97.3%) and 93.8% (85.2%, 97.5%) in children (5 studies).

CONCLUSIONS

Anti-tissue transglutaminase sensitivity appears to be sufficient to rule out coeliac disease in children. The high specificity of endomysial antibody in adults supports its use to rule in coeliac disease. This evidence underpins the current development of clinical guidelines for a serological diagnosis of coeliac disease. Studies in primary care are needed to evaluate serological testing strategies in this setting.