Coeliac Disease

Gut Coeliac disease is an inflammatory condition of the small intestine. It is characterised by flattening of the gut epithelium (villous atrophy), which can lead to malabsorption of nutrients. Gluten, a protein found in wheat, barley and rye, was recognised in the 1950s to play a role in coeliac disease. Symptoms often disappear when patients are placed on a gluten-free diet.

Many of the symptoms seen in coeliac disease sufferers are also common in other intestinal disorders. These symptoms include diarrhoea, abdominal distention, fatigue, iron/folate deficiency and weight loss amongst others. The symptoms are often more acute in paediatric patients.

Coeliac disease is an autoimmune disease caused by a genetically related increase in the activity of tissue transglutaminase (tTG), an enzyme found in the endomysial layer of the gut. This enzyme interacts with gliadin (a portion of the gluten molecule), triggering an immune response that causes the symptoms described above.

Testing Protocols

ELISA Indirect immunofluorescence assays (IFA) and enzyme immunoassays (EIA) are used for screening and quantitation of these autoantibodies.

These techniques have the advantage that they are non-invasive for the patient, unlike the intestinal biopsy. They are also useful in monitoring patients on a gluten free diet as levels of the antibodies involved in coeliac disease reduce in the absence of gluten.

IFA Screening

Non-rodent oesophagus sections are traditionally used to visualise Endomysial Antibodies (EMA). These antibodies will bind to antigens present in the endomysial layer of the oesophagus tissue.

A species-specific Fluorescein conjugate is recommended to reduce the amount of non-specific background fluorescence sometimes seen when using non-rodent tissue.

EIA Specificity Confirmation and Quantitation

The first enzyme immunoassays developed to quantify the antibodies responsible for causing coeliac disease were for anti-gliadin antibodies.

In 1997 the tTG enzyme was identified as the target antigen for endomysial antibodies¹ and EIAs were developed to quantify serum antibodies against it. Although anti-gliadin antibodies are found in coeliacs, they can also be found in other disorders, and studies have now shown anti-tTG antibodies are more specific for coeliac disease².

IgA and IgG antibodies

In most cases, the majority of the antibodies against coeliac antigens will be of the IgA isotype. It is therefore recommended that an IgA conjugate is used for their detection.

However, IgA deficiency affects 2 to 3% of coeliac disease sufferers. This is a 10 to 15 fold increase compared to IgA deficiency in the general population³.

It is therefore advised that patients who are IgA deficient, are also tested for IgG antibodies against the coeliac antigens.

Proposed Testing Protocol

References