Determination of anti-omega-gliadin antibodies in serologic tests for coeliac disease

Overlap of Characteristic Serological Antibodies in Rheumatoid Arthritis and Wheat-Related Disorders

Background and Aims

Rheumatoid arthritis (RA) and celiac disease (CD) are members of the autoimmune disease family while they have been shown to share multiple aspects in epidemiology and clinical manifestations. The aim of this study was to assess the presence of wheat protein antibodies in RA seropositive subjects and the presence of RA diagnostic markers in subjects with seropositive wheat-related disorders including CD.

Methods

Serum samples were collected from 844 subjects with joint pain and/or gastrointestinal symptoms and tested by a CD panel (anti-tTG and anti-DGP), a Wheat Zoomer (WZ) antibody panel (IgG/IgA to 14 wheat proteins), and a RA panel (anti-CCP and anti-RF). Retrospective analysis was completed using de-identified clinical data and test results.

Results

The prevalence of RA markers was first investigated in CD- or WZ-positive subjects and negative controls. 49 subjects were seropositive in the CD panel with 10 (20%) RA positivity. 605 subjects were seropositive in the WZ panel with 106 (18%) RA positivity. 222 subjects were seronegative in either panels with 12 (6%) RA positivity. Next, the frequency of the CD markers and the clinically relevant wheat protein antibodies were investigated in the RA-positive subjects and negative controls. 128 subjects in this cohort were seropositive in the RA panel with 10 (8%) CD positivity and 106 (83%) WZ positivity, compared to 716 RA seronegative controls with 39 (5%) CD positivity and 499 (70%) WZ positivity.

Conclusions

Our data presents an apparent trend of overlapped serological antibody biomarker positivity in RA and wheat-related disorders.

High Frequency of Extractable Nuclear Autoantibodies in Wheat-Related Disorders

Background and aims:

There has been broad interest to explore the presence of autoimmunity among wheat-sensitive individuals, but neither the pathogenesis nor the relevance has been established. In this study, we evaluated the frequencies and levels of autoantibodies, which are important biomarkers of autoimmunity, in subjects with wheat-related disorders and controls. Anti-nuclear antibodies (ANA) and the specific ones against extractable nuclear antigens (ENA) were investigated.

Methods:

A total of 713 subjects who showed symptoms related to wheat ingestion were addressed to Vibrant America Clinical Laboratory from December 2015 to November 2017. Serum samples were collected from all subjects and tested with a wheat protein antibody panel (IgG and IgA to 18 proteins at the peptide level) and an autoantibody panel (ANA by immunofluorescence analysis and 10 ENA antibodies). Retrospective analysis was completed using de-identified clinical data and test results.

Results:

In the retrospective analysis, 38 (5%) were seropositive in a Celiac Disease panel, 491 (83%) were seropositive in a wheat protein antibody panel “Wheat Zoomer,” and 84 (12%) were seronegative in both panels. Anti-nuclear antibodies were detected in similar portions of the celiac disease subjects (13%), the Wheat Zoomer–positive subjects (12%), and seronegative controls (15%), which is also very close to the reported occurrence of ANA positivity (15%) in the healthy population. The prevalence of anti-ENA was reported to be less than 2% in the general population; however, our study found it to be much higher in the celiac disease subjects (29%) and the wheat-sensitive subjects (27%), compared with a smaller proportion of seronegative controls (19%). The prevalence of anti-histone was especially prominent among the celiac disease subjects (73%) and the Wheat Zoomer–positive subjects (60%).

Conclusions:

High proportions of wheat-related disease subjects carry ENA antibodies that are important specific biomarkers of autoimmunity.

What are the sensitivity and specificity of serologic tests for celiac disease? Do sensitivity and specificity vary in different populations?

A number of serologic tests are available commercially for identifying individuals who require an intestinal biopsy examination to diagnose celiac disease (CD). The aim of this study was to determine which test, or combination of tests, was most sensitive and specific for this purpose. We performed a literature review of studies that determined the sensitivity and specificity of serologic tests for CD. Studies that compared biopsy examination-confirmed cases of CD with controls with normal intestinal histology were selected for analysis. Sensitivities and specificities for the antigliadin tests were highly variable. Immunoglobulin (Ig)G-based antigliadin (AGA) tests generally were poor in both parameters whereas the IgA-based test was poorly sensitive but more specific. The IgA endomysium (EMA-IgA) and tissue transglutaminase (TTG-IgA) tests were both highly sensitive and specific with values for both parameters exceeding 95% in most studies. There were no identifiable differences between adults and children with respect to these tests. There was no evidence that a combination of tests was better than a single test using either the EMA IgA or TTG IgA. Either the EMA-IgA or TTG-IgA test is most useful for identifying individuals with CD. The variability and generally lower accuracy associated with the AGA tests make them unsuitable for screening purposes. There is no advantage to using a panel of tests as opposed to a single test. Because these data were obtained largely from studies conducted in a research setting, it is possible the tests will be less accurate when used in the clinical setting.

The diagnostic accuracy of serologic tests for celiac disease: a systematic review

Clinicians are increasingly utilizing noninvasive serologic tests for the diagnosis and screening of celiac disease (CD). The aim of this study was to conduct a systematic review of the diagnostic performance of serologic tests for the diagnosis and screening of CD. Standard systematic review methodology was used. A literature search was conducted in MEDLINE (1966 to October 2003) and EMBASE (1974 to December 2003) databases. A weighted mean of the sensitivity and specificity along with 95% confidence intervals and summary receiver operating characteristic (ROC) curves were calculated. The pooled specificity of endomyseal antibody (EMA)-monkey esophagus (ME) or EMA-human umbilical cord (HU) was close to 100% in adults and children. The pooled specificity of transglutaminase antibody (tTG)-guinea pig (GP) and tTG-human recombinant (HR) were between 95% and 99%. IgA-EMA-ME demonstrated sensitivities of 96% and 97% in children and adults, respectively. EMA-HU demonstrated a similar sensitivity of 97% in children but 90% in adults. The pooled sensitivity of tTG-GP in adults and children was 90% and 93%, respectively. The sensitivity of tTG-HR was 98% and 96%, respectively. The performance of antigliadin antibody was inferior to that of EMA and tTG. EMA and tTG offer high sensitivity and specificity. The sensitivity of these tests appears to be lower than reported when milder histologic grades are used to define CD (below 90%). If true, the nearly perfect negative predictive value of these tests would drop. The positive predictive value of these tests is likely lower than reported when the tests are applied in low-prevalence populations.

Evaluation of coeliac disease serological markers in Down syndrome patients

BACKGROUND

The increased incidence of coeliac disease in patients with Down syndrome makes screening of coeliac disease in this population advisable.

AIM

Evaluation of efficiency of different serological markers to detect coeliac disease in Down syndrome patients.

PATIENTS

A total of 56 Down syndrome patients (aged: 1-17 years) were included in study.

METHODS

Patients were evaluated for both IgG and IgA anti-transglutaminase antibodies and for anti-gliadin IgA and IgG antibodies using either purified omega-gliadin, wheat ethanol extract or commercial gliadin. Patients who had at least one positive result were evaluated for antiendomysium antibodies using either monkey oesophagus or human umbilical cord by indirect immunofluorescence. Coeliac disease was diagnosed by typical histological changes on duodenal mucosa.

RESULTS

Increased levels of at least one anti-gliadin IgA and IgG antibody marker were found in 27 out of 56 cases (26 for IgG and 9 for IgA). 11/56 were positive for IgG anti-transglutaminase antibodies and two of them were also positive for IgA anti-transglutaminase antibodies and anti-endomysium antibodies. These two patients were finally diagnosed as coeliacs. Gliadin antigenic fractions employed produced differences in the performance of the anti-gliadin IgA and IgG antibody test. The use of commercial gliadin or wheat ethanol extract showed low sensitivity in IgA anti-gliadin IgA and IgG antibody determination, whereas good sensitivity and specificity were observed with omega-gliadins. IgG anti-transglutaminase antibodies showed a high proportion of false positive results (9 out of 56), whereas anti-endomysium antibodies and IgA anti-transglutaminase antibodies presented an excellent correlation with presence of active coeliac disease.

CONCLUSIONS

Two out of 56 Down syndrome patients were diagnosed as coeliacs, corresponding to an incidence of 3.6%. The use of omega-gliadin presented the best efficiency in anti-gliadin IgA and IgG antibody determination whereas IgA anti-transglutaminase antibodies and anti-endomysium antibody determination showed an absolute correlation with presence of active coeliac disease.