Clinical evaluation of the BioPlex 2200 Celiac IgA and IgG Kits — A novel multiplex screen incorporating an integral check for IgA deficiency

Tissue transglutaminase immunoglobulin A exceeds endomysial antibody in specificity of celiac diagnosis at ≥10 times the upper limit of normal

OBJECTIVE

Serologic diagnosis using tissue transglutaminase immunoglobulin A (TTG-IgA) and endomysial antibody (EMA) is being integrated into the care of pediatric patients with positive screening for celiac disease. The purpose of this study was to assess the utility of EMA in pediatric patients being considered for serologic diagnosis.

METHODS

Patients with TTG-IgA testing performed between May 1, 2022 and April 30, 2023 and with subsequent duodenal biopsy within 6 months were included. TTG-IgA serum samples were frozen and sent for EMA testing and titer. EMA was evaluated for positivity and TTG-IgA (normal <15 u/mL) for elevation <10 times (10x) the upper limit of normal (ULN) and ≥10x ULN (≥150 u/mL). Sensitivity and specificity of EMA and TTG-IgA were calculated using biopsy histology as the gold standard.

RESULTS

Four hundred and eighty-six patients were included. The sensitivity and specificity of TTG-IgA ≥15 u/mL was 87.5% and 95.4% while EMA was 77.5% and 97.3%. For patients with TTG-IgA ≥10x ULN the specificity was 99.3%. The positive predictive value of TTG-IgA at ≥10x ULN was 91.4% and for EMA was 83.6%. All three patients with false positive TTG-IgA ≥10x ULN also had false positive EMA, and two of these patients had type 1 diabetes mellitus.

CONCLUSIONS

TTG-IgA has greater sensitivity at the screening threshold of ≥15 u/mL and greater specificity and positive predictive value at ≥10x ULN than EMA. TTG-IgA at ≥10x ULN is superior to EMA for the serologic diagnosis of celiac disease.

Accuracy of Serological Screening for the Diagnosis of Celiac Disease in Type 1 Diabetes Children

Background and Objectives: Patients with type 1 diabetes (T1D) are considered at high-risk for developing celiac disease (CD). The purpose of our study was to determine the prevalence of CD among children who were followed in our unit for T1D using the latest ESPGHAN guidelines, and avoiding intestinal biopsies in some of the children. Materials and Methods: We performed a prospective monocentric study, which included 663 T1D children between June 2014 and June 2016. We considered CD according to serological (tissue transglutaminase (TGAs) and endomysium antibodies) results. Children were included either at the time of T1D diagnosis or during their follow up. We looked for clinical and biochemical signs of CD, and for T1D characteristics. Results: The children's ages ranged from 11 months to 18 years. CD was confirmed in 32 out of 663 patients with T1D, with a prevalence of 4.8%. CD was excluded in 619 children and remained uncertain for 12 children, who had positive TGAs without the required criteria. We found that 95% of T1D children express HLA-DQ2 and/or -DQ8, which was 2.4 times higher than in the general population. Conclusions: An intestinal biopsy could be avoided to confirm CD in the majority of T1D children. Silent forms of CD are frequent and screening is recommended for all patients. Importantly, repeated TGA assessment is required in HLA genetically predisposed T1D patients, while it is unnecessary in the 5% who are HLA-DQ2 and -DQ8 negative.

Time to normalisation of tissue transglutaminase in paediatric coeliac disease is dependent on initial titre and half of patients will normalise within 12 months

BACKGROUND

Coeliac disease (CD) is common. Response to a gluten-free diet is assessed through serial measurement of tissue transglutaminase (TTG) antibody titre. However, the relationship of TTG titres to symptoms and the speed of normalisation is poorly understood.

METHODS

Patients seen in 2020, and under follow-up in the Southampton CD clinic, had blood results, growth measures and symptom data collated. Time to normalisation, predictors of normalisation and relationship of TTG to growth/symptoms were assessed.

RESULTS

57 patients were included. All had TTG results from the time of diagnosis and follow-up. All families reported dietary compliance.Median TTG at diagnosis was 100 μ/L (range 0.3-4360), 94.7% of the patients had symptoms compatible with CD. At 6-12 months after diagnosis, the median TTG was 3.8 μ/mL (range 0.3-133). In terms of response, 29 of the 57 patients (50.9%) had a TTG below 4 μ/mL (upper normal limit). A further 25 patients (43.9%) had a TTG<10 times the upper limit of normal. Ten patients (17.5%) had a persistently high TTG (median=8.55 μ/mL, range 4.1-303) after >12 months.TTG at diagnosis was correlated with TTG at 6-12 months, β=0.542, p=0.000016. Patients with TTG<10 times the upper limit of normal at diagnosis group were more likely to have normalised at 6-12 months compared with >10 times normal (85% vs 32.4%, p=0.0015). TTG titres did not correlate with growth measures (Z-scores) at diagnosis or at follow-up.

CONCLUSIONS

Normalisation of TTG levels occurs within 6-12 months for around half of patients. Higher TTG levels at diagnosis take longer to normalise. The role of compliance is unclear.

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.

Real-life Performance of Multiplex Celiac Antibody Test in the Diagnosis of Pediatric Celiac Disease

OBJECTIVE

Tissue-transglutaminase antibodies (TGA) may be used to diagnose celiac disease (CD) without biopsy in selected cases. We aimed to investigate real-life performance of a CD serology automated analyzer (Bioplex2200), and to explore the correlation between TGA levels and intestinal biopsies in children.

METHODS

A retrospective review was performed in 2 pediatric gastroenterological centers, between November 1, 2018 and April 1, 2020 and included patients with both TGA serology testing and duodenal biopsies. Retrieved data included patients' demographics, medical background, TGA levels, and biopsy results.

RESULTS

Overall, 538 children were evaluated, 256 with positive TGA (68.4% girls, median age 6.4 years), and 282 with negative TGA (53.9% girls, median age 13.4 years). Among patients with positive TGA, intestinal biopsies confirmed CD in 219 (85.5%). Overall, positive serology with normal histology was found in 14.5% of the cohort, with 52%; 21.6%; 21.1%; and 4.2% in TGA ranges of 1 to 3 times upper limit of normal (ULN); 3 to 5 ULN; 5 to 10 ULN; and above 10 times ULN, respectively, P < 0.001. Area under the receiver-operating characteristic curve (AUC) was 0.963 (95% CI 0.947-0.980). Among patients with positive TGA, 216 (84.4%) had positive anti-endomysial antibodies. In this sub-group, the overall diagnostic performance was inferior, with AUC of 0.737 (95% CI 0.834-0.839).

CONCLUSIONS

The Multiplex TGA assay had a very high diagnostic accuracy in real-life. Among patients with positive TGA, adding EMA did not improve the diagnostic performance of the test. False-positive rates differed between different ranges of TGA and were low with TGA above 10 times ULN.

Evaluation of BioPlex 2200 tTG-IgA Diagnostic Performance for Serology-Based Diagnosis of Celiac Disease

OBJECTIVES

Forgoing biopsy for the diagnosis of celiac disease in children with tissue transglutaminase immunoglobulin A (tTG-IgA) levels greater than or equal to 10 times the upper limit of normal (≥10×ULN) has been advocated by the European Society of Paediatric Gastroenterology, Hepatology and Nutrition.

METHODS

Our retrospective study tested the specificity and positive predictive value (PPV) of the BioPlex 2200 assay (Bio-Rad Laboratories) in diagnosing celiac disease at the ≥10×ULN tTG-IgA threshold, which is ≥150 U/mL (negative <15 U/mL). We used the tTG-IgA and duodenal biopsy results within 6 months following tTG-IgA measurements from 542 patients who had any number of duodenal biopsy fragments, of whom 165 patients had 5 or more tissue fragments. Sensitivity and specificity of the test were calculated using histology as the gold standard for Marsh class 2 and above.

RESULTS

For histopathologic findings in the duodenum with Marsh 2 and higher, the specificity and PPV of the BioPlex 2200 at ≥10×ULN tTG-IgA were 99.5% and 95.4% using all biopsies and 97.9% and 94.9% for biopsies with 5 or more tissue fragments.

CONCLUSIONS

Should clinical considerations preclude endoscopy, the BioPlex 2200 assay at ≥10×ULN TTG-IgA could be considered highly suggestive of disease.

Clinical, Methodological, and Practical Considerations for Algorithmic Testing in Autoimmune Serology

BACKGROUND

Autoimmune serology tests are central to the classification, screening, diagnosis, and monitoring of a variety of autoimmune disorders. To improve the appropriateness of serologic evaluation and support laboratory resource utilization, reflex testing approaches have been proposed and implemented across clinical laboratories. Reflex testing involves a staged approach where an initial test result triggers subsequent tests based on prespecified rules.

CONTENT

Various reflex testing approaches in the context of antinuclear antibody-associated rheumatic disease, antineutrophil cytoplasmic autoantibody-associated vasculitis, celiac disease, and myasthenia gravis are reviewed here. Clinical, analytical, and practical considerations of reflex testing implementation are addressed as well as associated limitations and challenges.

SUMMARY

Serology reflex testing algorithms for the evaluation of autoimmune diseases can support clinical diagnosis and laboratory resource use but may be challenging to implement and are often applied variably across institutions. Assessments of evidence-driven guidelines, clinical impact, and impact on laboratory workflow are essential to this task.

Pediatric Celiac Disease: A Review of Diagnostic Testing and Guideline Recommendations

BACKGROUND

The history of how our knowledge of celiac disease (CD) evolved points to its importance in children. Although it is now appreciated that CD can present at any age, it was originally thought to occur only in children and, if untreated, led to serious consequences.

CONTENT

This review includes a brief discussion of small bowel physiology and the pathogenesis of CD. Next, the varied clinical presentations of CD in children are reviewed, including both gastrointestinal and nongastrointestinal manifestations and how these contribute to the difficulty in diagnosis. In addition, information on specific conditions that are associated with CD is presented, particularly as it applies to diagnostic testing of apparently asymptomatic children. The review will also focus on diagnostic testing available for CD and their general performance characteristics. The review will end with a comparison between published guidelines from the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition and the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition for diagnosis of pediatric CD. In particular, this review will focus on differences in the incorporation of serologic and genetic testing, and the role of biopsies in the pediatric population.

SUMMARY

It is important for laboratorians to understand the evolution of diagnostic guidelines for pediatric CD and how serologic and genetic testing are being applied to and interpreted in this particular patient group.

Detection and Sourcing of Gluten in Grain with Multiple Floating-Gate Transistor Biosensors

We report a chemically tunable electronic sensor for quantitation of gluten based on a floating-gate transistor (FGT) architecture. The FGTs are fabricated in parallel and each one is functionalized with a different chemical moiety designed to preferentially bind a specific grain source of gluten. The resulting set of FGT sensors can detect both wheat and barley gluten below the gluten-free limit of 20 ppm (w/w) while providing a source-dependent signature for improved accuracy. This label-free transduction method does not require any secondary binding events, resulting in a ca. 45 min reduction in analysis time relative to state-of-the-art ELISA kits with a simple and easily implemented workflow.

Current screening approaches for antibody deficiency

PURPOSE OF REVIEW

Diagnostic delay is a major problem for rare diseases including primary antibody deficiency (PAD). The aim of this review is to discuss the opportunities and challenges of current and future screening approaches for antibody deficiency, to reduce the delay and its impact on patients. (Figure is included in full-text article.)

RECENT FINDINGS

Diagnostic delay in PAD is known to result in increased morbidity, mortality, and permanent functional impairment. Approaches to prevent this have been only partially successful and the delay may still be many years as the clinical presentation of PAD is highly variable and may be at any age, making screening difficult. Patients often have numerous healthcare encounters generating repeated cycles of laboratory and clinical data before the diagnosis is made. Low immunoglobulin levels result in alterations in laboratory tests not directly aimed at measuring immunoglobulins. We describe these and highlight the growing evidence in support of using calculated globulin which is part of the liver function test profile as a screening tool for antibody deficiency. Additional approaches include using embedded algorithms to analyse data generated by repeated clinical encounters (e.g. infections, antibiotics, cytopenias), potentially in combination with laboratory results such as calculated globulin, to help bring forward the diagnosis of PAD in patients in whom this has not yet been considered.

SUMMARY

There is a strong case for the use of calculated globulin in screening for antibody deficiency. Further work is required to integrate laboratory results with clinical data to reduce diagnostic delay in patients with hitherto unsuspected antibody deficiency.

Celiac disease: advances in diagnosis

Celiac disease (CD) is characterized by small intestinal damage, which is mediated by a gluten-driven inflammatory response. Establishing a robust diagnosis is critical for improved quality of life and prevention of co-morbidities, although treatment is associated with a substantial life-long burden of care for patients and families. Unfortunately, CD remains a challenging diagnosis. As awareness of the disease increases, more diagnoses of CD are being made by primary care physicians. In fact, many patients may not present to a gastroenterologist because their symptoms are not clearly linked to a gastrointestinal pathology. Also, many patients are starting a gluten-free diet without prior testing, a circumstance that leads to even more confusion. Lastly, the number of serologic and genetic tests, and the role of endoscopy, can be confusing. The purpose of this review is to examine diagnostic testing strategies, focusing on published guidelines, for the evaluation of patients with suspected CD.

Automation, consolidation, and integration in autoimmune diagnostics

Over the past two decades, we have witnessed an extraordinary change in autoimmune diagnostics, characterized by the progressive evolution of analytical technologies, the availability of new tests, and the explosive growth of molecular biology and proteomics. Aside from these huge improvements, organizational changes have also occurred which brought about a more modern vision of the autoimmune laboratory. The introduction of automation (for harmonization of testing, reduction of human error, reduction of handling steps, increase of productivity, decrease of turnaround time, improvement of safety), consolidation (combining different analytical technologies or strategies on one instrument or on one group of connected instruments) and integration (linking analytical instruments or group of instruments with pre- and post-analytical devices) opened a new era in immunodiagnostics. In this article, we review the most important changes that have occurred in autoimmune diagnostics and present some models related to the introduction of automation in the autoimmunology laboratory, such as automated indirect immunofluorescence and changes in the two-step strategy for detection of autoantibodies; automated monoplex immunoassays and reduction of turnaround time; and automated multiplex immunoassays for autoantibody profiling.

ELISA in the multiplex era: potentials and pitfalls

Multiplex immunoassays confer several advantages over widely adopted singleplex immunoassays including increased efficiency at a reduced expense, greater output per sample volume ratios and higher throughput predicating more resolute, detailed diagnostics and facilitating personalised medicine. Nonetheless, to date, relatively few protein multiplex immunoassays have been validated for in vitro diagnostics in clinical/point-of-care settings. This review article will outline the challenges, which must be ameliorated prior to the widespread integration of multiplex immunoassays in clinical settings: (i) biomarker validation; (ii) standardisation of immunoassay design and quality control (calibration and quantification); (iii) availability, stability, specificity and cross-reactivity of reagents; (iv) assay automation and the use of validated algorithms for transformation of raw data into diagnostic results. A compendium of multiplex immunoassays applicable to in vitro diagnostics and a summary of the diagnostic products currently available commercially are included, along with an analysis of the relative states of development for each format (namely planar slide based, suspension and planar/microtitre plate based) with respect to the aforementioned issues.

Experimental hookworm infection and gluten microchallenge promote tolerance in celiac disease

BACKGROUND

Celiac disease (CeD) is a common gluten-sensitive autoimmune enteropathy. A gluten-free diet is an effective treatment, but compliance is demanding; hence, new treatment strategies for CeD are required.

OBJECTIVE

Parasitic helminths hold promise for treating inflammatory disorders, so we examined the influence of experimental hookworm infection on the predicted outcomes of escalating gluten challenges in CeD subjects.

METHODS

A 52-week study was conducted involving 12 adults with diet-managed CeD. Subjects were inoculated with 20 Necator americanus larvae, and escalating gluten challenges consumed as pasta were subsequently administered: (1) 10 to 50 mg for 12 weeks (microchallenge); (2) 25 mg daily + 1 g twice weekly for 12 weeks (GC-1g); and (3) 3 g daily (60-75 straws of spaghetti) for 2 weeks (GC-3g). Symptomatic, serologic, and histological outcomes evaluated gluten toxicity. Regulatory and inflammatory T cell populations in blood and mucosa were examined.

RESULTS

Two gluten-intolerant subjects were withdrawn after microchallenge. Ten completed GC-1g, 8 of whom enrolled in and completed GC-3g.

PRIMARY OUTCOMES

median villous height-to-crypt depth ratios (2.60-2.63; P = .98) did not decrease as predicted after GC-1g, and the mean IgA-tissue transglutaminase titers declined, contrary to the predicted rise after GC-3g.

SECONDARY OUTCOMES

quality of life scores improved (46.3-40.6; P = .05); celiac symptom indices (24.3-24.3; P = .53), intra-epithelial lymphocyte percentages (32.5-35.0; P = .47), and Marsh scores were unchanged by gluten challenge. Intestinal T cells expressing IFNγ were reduced following hookworm infection (23.9%-11.5%; P = .04), with corresponding increases in CD4(+) Foxp3(+) regulatory T cells (0.19%-1.12%; P = .001).

CONCLUSIONS

Necator americanus and gluten microchallenge promoted tolerance and stabilized or improved all tested indices of gluten toxicity in CeD subjects.