Advice before testing and recommended tests

It is important to inform people undergoing testing for coeliac disease that in order to get accurate test results, they should continue to eat a gluten containing diet before and during the diagnosis process. NICE recommends including gluten in more than one meal a day for at least six weeks before testing. It is not possible to recommend a specific amount of gluten.

The person should not start a gluten free diet until diagnosis is confirmed by a specialist, even if the results of a serological test are positive.

If people who have restricted their gluten intake or excluded gluten from their diet are unable to reintroduce gluten into their diet before testing, refer the patient to a gastroenterologist and explain that it may be difficult to confirm their diagnosis by intestinal biopsy.

Recommended tests

Coeliac disease is diagnosed by serological testing and endoscopic intestinal biopsy. Someone with coeliac disease produces tissue transglutaminase antibodies (tTGA) and endomysial antibodies (EMA) when gluten is ingested.

The NICE guideline on recognition, assessment and management of coeliac disease provides recommendations on the appropriate tests when coeliac disease is suspected.

When requesting tests for young people and adults, laboratories should:

• test for total immunological immunoglobin A (IgA) and IgA tissue transglutaminase as a first choice test
• use IgA endomysial antibodies (EMA) if IgA tTG is weakly positive
• consider using IgG EMA, IgG deamidated gliadin peptide (DGP) or IgG tTG in cases of IgA deficiency. 

When requesting tests for children, laboratories should:

• test for total IgA and IgA tTG, as first choice test
• consider using IgG EMA, IgG DGP or IgG tTG in cases of IgA deficiency.

Patients with a positive blood test and those with negative antibodies where coeliac disease is suspected should be referred to a gastroenterologist or, in the case of children, a paediatric gastroenterologist or paediatrician with a specialist interest in gastroenterology.

For children a biopsy may not be necessary in every case. A guideline published by the British Society of Paediatric Gastroenterology, Hepatology and Nutrition (BSPGHAN) and Coeliac UK recommends children with symptoms of coeliac disease whose blood tests show a high level of antibodies and have the genes for coeliac disease may not need to have a biopsy to confirm the diagnosis.

More information on diagnosis in children is available on our website.

IgA deficiency

Coeliac disease is strongly associated with particular variations of the human leukocyte antigen (HLA) DQ gene. Research has shown that the HLA-DQ2 and HLA-DQ8 variants are almost always present in people with coeliac disease of white, Northern European background. These variants probably play a similar role in other ethnic groups, although this is less clear.

Testing for the HLA DQ2 and HLA DQ8 variants alone cannot be used to diagnose coeliac disease as these genes are present in around a third of the UK population including people who do not have coeliac disease. NICE recommend to only consider using HLA DQ2 (DQ2.2and DQ2.5) DQ8 testing in diagnosis of coeliac disease in specialist settings. For example children who are not having a biopsy or people who have already limited gluten from the diet and choose not to have a gluten challenge.

More information on diagnosis in children is available on our website.