New screening tests enrich anti-transglutaminase results and support a highly sensitive two-test based strategy for celiac disease diagnosis

Deamidated Gliadin Antibodies: Do They Add to Tissue Transglutaminase-IgA Assay in Screening for Celiac Disease?

OBJECTIVES

Use of deamidated gliadin peptide (DGP) test kits as adjunctive to tissue-transglutaminase-IgA (TTG-IgA) for the diagnosis of celiac disease (CD) has been a controversial issue. The objectives of our study were to evaluate the diagnostic performance of DGP antibodies compared with TTG-IgA and to evaluate the correlation between DGP-antibody titers and degree of enteropathy.

METHODS

We included children who underwent endoscopy and biopsies because of positivity of any of the serology tests in the "celiac profile" (TTG-IgA, DGP-IgA, and DGP-IgG) from 2012 to 2019. We divided children into clinically suspected cases of CD (group 1) and asymptomatic cases screened as they were from a high-risk group (group 2).

RESULTS

Group 1 constituted 52 children and group 2 included 81 children (76 type-1 diabetes [T1D]). The sensitivity and positive-predictive value (PPV) of DGP-IgG in group 1 (90%, 98%) and group 2 (91%, 85.5%) were comparable with TTG-IgA (98%, 92% in group 1; 100%, 80% in group 2). By adding DGP-IgG to TTG-IgA, the performance of TTG-IgA has improved marginally in group 1 (sensitivity 100%, PPV 92.3%). All cases with DGP-IgG titer 2 times ULN in group 1, and >4 times ULN in group 2 had villous atrophy. All T1D patients with TTG IgA >10 times ULN had villous atrophy.

CONCLUSIONS

DGP-IgG assay did not add to the performance of TTG-IgA. DGP-IgG titer correlated with enteropathy. The diagnosis of CD can be made in asymptomatic T1D child with TTG-IgA titer >10 times ULN and positive endomyseal antibodies.

Estimating the Impact of Verification Bias on Celiac Disease Testing

GOAL

The goal of this study was to estimate the impact of verification bias on the diagnostic accuracy of immunoglobulin A tissue transglutaminase (IgA tTG) in detecting celiac disease as reported by an authoritative meta-analysis, the 2016 Comparative Effectiveness Review (CER).

BACKGROUND

Verification bias is introduced to diagnostic accuracy studies when screening test results impact the decision to verify disease status.

MATERIALS AND METHODS

We adjusted the sensitivity and specificity of IgA tTG reported by the 2016 CER with the proportion of IgA tTG positive and negative individuals who are referred for confirmatory small bowel biopsy. We performed a systematic review from January 1, 2007, to July 19, 2017, to determine these referral rates.

RESULTS

The systematic review identified 793 articles of which 9 met inclusion criteria (n=36,477). Overall, 3.6% [95% confidence interval (CI): 1.1%-10.9%] of IgA tTG negative and 79.2.2% (95% CI: 65.0%-88.7%) of IgA tTG positive individuals were referred for biopsy. Adjusting for these referral rates the 2016 CER reported sensitivity of IgA tTG dropped from 92.6% (95% CI: 90.2%-94.5%) to 57.1% (95% CI: 35.4%-76.4%) and the specificity increased from 97.6% (95% CI: 96.3%-98.5%) to 99.6% (95% CI: 98.4%-99.9%).

CONCLUSIONS

The CER may have largely overestimated the sensitivity of IgA tTG due to a failure to account for verification bias. These findings suggest caution in the interpretation of a negative IgA tTG to rule out celiac disease in clinical practice. More broadly, they highlight the impact of verification bias on diagnostic accuracy estimates and suggest that studies at risk for this bias be excluded from systematic reviews.

Influence of Age and Type 1 Diabetes Mellitus on Serological Test for Celiac Disease in Children

PURPOSE

Serological tests of tissue transglutaminase (TTG) and deamidated gliadin (DGP) antibodies for celiac disease diagnosis show conflicting correlation with histology in young children and in type 1 diabetes mellitus (T1DM). Tests' ability to predict histology and cutoff values based on age and T1DM was evaluated.

METHODS

A retrospective study of children who had celiac serological tests between 6/1/2002 and 12/31/2014 at a pediatric hospital.

RESULTS

TTG IgA displayed similar results in predicting histology between <4.0 and ≥4.0 years age groups with sensitivity 98% and 93%, and specificity 88% and 86%, respectively. In children <4.0 years old, sensitivity for DGP antibodies was 100% and specificity 94%; in ≥4.0 years age groups, sensitivity was 60%, 88% for DGP IgA and IgG and specificity 95%, 96%, respectively. TTG IgA had low specificity in patients with T1DM compared with non-T1DM, 42% vs. 91%. Positive TTG IgA with normal histology was associated with higher T1DM prevalence at 36% compared with negative tests at 4%. Finally, the TTG IgA cutoff value was higher in T1DM at 36 vs. 16.3 units in non-T1DM. DGP IgG cutoff showed similar values between age groups; TTG IgA and DGP IgA cutoffs were lower in <4.0 years at 8.3 and 11.9 units than ≥4.0 years at 23.4 and 19.9, respectively.

CONCLUSION

TTG IgA is sufficient for the <4.0 years age group and DGP antibodies had no advantage over TTG IgA in older children. The cutoff value to determine a positive TTG IgA should be higher for children with T1DM.

Recent advances in biosensors for diagnosis of celiac disease: A review

Celiac disease (CD) is an intestinal issue activated by the inappropriate immune reaction towards gluten protein of wheat, rye, barley, oats, and autoantigen, tissue transglutaminase. Regardless of the accessibility of immunochemical conventions for research facility analysis of CD, there is as yet a need of speedier, less expensive, and simpler devices for diagnosing CD. This review concentrates on progresses in biosensors for diagnosing CD in perspective of the scaled down hardware, multianalyte discovery and low sample volume necessity. Various recently developed biosensors in this field are presented.

Ultrasensitive transglutaminase based nanosensor for early detection of celiac disease in human

A GQD/PAMAM nanohybrid modified on gold nanoparticles (AuNP) embedded in multiwalled carbon nanotubes (MWCNT) based immunosensor was developed for detection of celiac disease in human. The AuNP embedded in MWCNT were linked with thiol groups of cysteine and amino groups were further coupled with carboxyl moieties of graphene quantum dots (GQDs) using EDC-NHS cross-linking chemistry. To enhance the sensitivity of the sensor, polyamidoamine (PAMAM) dendrimer was attached with GQDs through carbodiimide coupling. The tissue transglutaminase (tTG) antigen was immobilized on PAMAM to form nanoprobe for sensing specific anti-tissue transglutaminase (anti-tTG) antibodies (immunoglobin A isotype) in human serum. The electrochemical changes after specific binding of antibody with antigen was measured cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The modifications in sensor surface were characterized using FE-SEM. The sensor is highly specific to anti-tissue transglutaminase antibodies and showed negligible response to non-specific serum proteins. The sensitivity of the sensor was 1297.14μA/cm²/pg with DPV and lower limit of detection of anti-tissue transglutaminase antibody was found 0.1fg per 6μl.

A Canadian Study toward Changing Local Practice in the Diagnosis of Pediatric Celiac Disease

Background. The European Society for Pediatric Gastroenterology, Hepatology and Nutrition endorses serological diagnosis (SD) for pediatric celiac disease (CD). The objective of this study was to pilot SD and to prospectively evaluate gastrointestinal permeability and mucosal inflammation at diagnosis and after one year on the gluten-free diet (GFD). We hypothesized that SD would be associated with similar short term outcomes as ED. Method. Children, 3-17 years of age, referred for possible CD were eligible for SD given aTTG level ≥200 U/mL, confirmed by repeat aTTG and HLA haplotypes. Gastrointestinal permeability, assessed using sugar probes, and inflammation, assessed using fecal calprotectin (FC), at baseline and after one year on a GFD were compared to patients who had ED. Results. Enrolled SD (n = 40) and ED (n = 48) patients had similar demographics. ED and SD groups were not different in baseline lactulose: mannitol ratio (L : M) (0.049 versus 0.034; p = 0.07), fractional excretion of sucrose (%FES; 0.086 versus 0.092; p = 0.44), or fecal calprotectin (FC; 89.6 versus 51.4; p = 0.05). At follow-up, urine permeability improved and was similar between groups, L : M (0.022 versus 0.025; p = 0.55) and %FES (0.040 versus 0.047; p = 0.87) (p > 0.05). FC improved but remained higher in the SD group (37.1 versus 15.9; p = 0.04). Conclusion. Patients on the GFD showed improved intestinal permeability and mucosal inflammation regardless of diagnostic strategy. This prospective study supports that children diagnosed by SD have resolving mucosal disease early after commencing a GFD.

Serologic assay for diagnosis of celiac disease based on a patient-derived monoclonal antigliadin antibody

BACKGROUND & AIMS

Patients with celiac disease can be identified based on the detection of serum antibodies to deamidated gliadin peptides (DGPs). Recombinant human monoclonal antibodies (hmAb) against gliadin are produced by cloning antibody genes from single IgA-producing plasma cells isolated from lesions of patients with celiac disease. We developed an assay to identify patients with celiac disease based on the ability of antibodies from their serum to inhibit the binding of a gliadin-specific hmAb (1002-1E03) to a specific peptide antigen (inhibition assay).

METHODS

We selected 2 peptides (a 34-mer and a 26-mer) found in ω-gliadins and low-molecular-weight glutenins that had been identified as specific targets of the hmAb 1002-1E03 from a digest of gliadin treated by transglutaminase 2. These peptides contained repeat sequence motifs; their interaction with hmAb 1002-1E03 was assessed in an amplified luminescent proximity homogeneous inhibition assay. We also tested peptides we created that included 3 repeated sequence motifs. Serum samples from untreated patients diagnosed with celiac disease (n = 106) and 2 control groups (198 blood donors, 151 patients with Crohn's disease) were analyzed using the assay, as well as in conventional commercial assays that measure IgA against transglutaminase 2 (TG2) or IgG against DGP.

RESULTS

In our inhibition assays, the 34-mer peptide showed the best results, and identified patients with celiac disease with 86.8% sensitivity and 98.6% specificity. Its diagnostic accuracy was comparable with that of commercial anti-DGP IgG (sensitivity, 87.9%; specificity, 98.0) and anti-TG2 IgA (sensitivity, 81.1%; specificity, 98.9) assays, and it detected most of the patients with anti-TG2 IgA-negative celiac disease without a significant decrease in specificity. Combined use of the anti-ω34 and the anti-TG2 assays produced specificity and sensitivity values of 95.3% and 98.0%, respectively.

CONCLUSIONS

We developed an antigliadin inhibition assay that identifies patients with celiac disease with high levels of specificity and sensitivity. It may prove useful as an adjunct to the current assay for anti-TG2 IgA.

Celiac disease is not increased in women with hip fractures and low vitamin D levels

OBJECTIVE

Celiac disease is associated with decreased bone density; however, the risk of fractures in celiac disease patients is unclear. We compared the prevalence of celiac disease between a group of women with hip fractures and a group of women undergoing elective joint replacement surgery and the association between celiac disease and vitamin D levels.

METHODS

Two hundred eight community dwelling and postmenopausal women were recruited from Boston, MA (n=81) and Baltimore, MD (n=127). We measured tissue transglutaminase IgA by ELISA to diagnose celiac disease and 25-hydroxyvitamin D (25(OH)D) levels by radioimmunoassay in both women with hip fractures (n=157) and a control group (n=51) of total hip replacement subjects from Boston. Subjects were excluded if they took any medications or had medical conditions that might affect bone.

RESULTS

Median serum 25(OH)D levels were significantly lower (p< 0.0001) in the hip fracture cohorts compared to the elective joint replacement cohort (14.1 ng/ml vs. 21.3 ng/ml, respectively). There were no differences in the percentage of subjects with a positive tissue transglutaminase in the women with hip fractures versus the control group (1.91% vs. 1.96%, respectively).

CONCLUSION

Vitamin D levels are markedly reduced in women with hip fractures, however hip fracture patients did not show a higher percentage of positive tissue transglutaminase levels compared with controls. These data suggest that routine testing for celiac disease among hip fracture patients may not be necessary in the absence of clinical signs and symptoms, although data from larger studies among hip fracture subjects are needed.

Antibodies against deamidated gliadin peptides and tissue transglutaminase for diagnosis of pediatric celiac disease

OBJECTIVES

The aim of the present study was to evaluate diagnostic performance and actual costs in clinical practice of immumoglobulin (Ig)G/IgA deamidated gliadin peptide antibodies (DGP) as a complement to IgA antibodies against tissue transglutaminase (tTG) for the diagnosis of pediatric celiac disease (CD).

METHODS

All of the consecutive patients younger than 18 years tested for tTG and/or DGP, who underwent duodenal biopsy because of suspected CD in Stockholm and Gothenburg, Sweden, from 2008 to 2010, were included. Medical records were reviewed.

RESULTS

Of 537 children who underwent duodenal biopsy, 278 (52%) had CD. A total of 71 (13%) were younger than 2 years and 16 (4%) had IgA deficiency. Sensitivity and specificity for tTG were 94% and 86%, respectively. Corresponding values for DGP were 91% and 26%. Positive predictive values (PPV) were 88% for tTG and 51% for DGP. There were 148 children who were tTG-negative and DGP-positive, of which only 5% (8/148) had villous atrophy. Among children younger than 2 years with normal IgA, PPV was 96% (25/26) for tTG and 48% (24/50) for DGP. In 16 IgA-deficient children, 11 were DGP positive, of which 5 had CD (PPV 45%). Eight of 278 cases of CD would possibly have been missed without DGP. The cost of adding DGP and consequently more biopsies to be able to detect 8 extra cases of CD was [Euro sign]399,520 or [Euro sign]49,940 per case.

CONCLUSIONS

For diagnosing CD, tTG is superior to DGP, even in children younger than 2 years. Combining tTG and DGP does not provide a better tradeoff between number of missed cases of CD, number of unnecessary duodenal biopsies, and cost than tTG alone.

Autoimmune-polyendocrinopathy-candidiasis-ectodermal-dystrophy in Calabria: clinical, immunological and genetic patterns

Autoimmune polyendocrinopathy-candidiasis-ectodermal- dystrophy (APECED), also known as autoimmune polyendocrine syndrome type 1 (APS-1), is a very rare disease. Diagnosis requires the presence of at least two of three major clinical features: chronic mucocutaneous candidiasis, chronic hypoparathyroidism, and Addison's disease.

DESIGN

In this study, we analyzed Autoimmune Regulator (AIRE) gene mutations and genotype-phenotype correlation in APECED patients originating from Calabria, a region in the south of Italy.

PATIENTS AND METHODS

Four patients and their first-degree relatives were evaluated for clinical manifestations, autoantibody presence and AIRE gene mutations.

RESULTS

Three patients carried a homozygous W78R mutation on exon 2, typical of patients with APECED from Apulia; the fourth patient had a homozygous R203X mutation on exon 5, typical of APECED patients from Sicily. Clinical disease expression showed wide variability. Analysis of relatives allowed the identification of 6 heterozygotes, none of whom showed major findings of APECED.

CONCLUSIONS

No AIRE gene mutations specific to Calabria were found in patients with APS-1, but mutations similar to those in patients from Apulia and Sicily. Heterozygosity for AIRE gene mutation is not associated with major findings of APECED.

Diagnosis of celiac disease

This article reviews issues related to identifying the appropriate patient to test for celiac disease, the performance characteristics of serologic testing, the role of gene testing for human leukocyte antigen DQ2 and DQ8 haplotypes, and issues related to the performance of small intestinal biopsy. The article concludes with a review of special diagnostic considerations in pediatric patients.