Diagnosis of coeliac disease

The National Institute of Health and Care Excellence (NICE) released a guideline on the recognition of coeliac diseaseA condition where a person is unable to eat gluten as it makes their body attack itself. on 27 May 2009.(1) The guideline outlines the symptoms and patients at risk of coeliac disease, as well as evidence on how to identify people with the condition.

A new guideline for the diagnosis and management of coeliac disease in children has been published this year by the British Society of Paediatric Gastroenterology, Hepatology and Nutrition (BSPGHANBritish Society of Paediatric Gastroenterology, Hepatology and Nutrition - provides professional leadership, promotes standards of care for children with gastrointestinal, liver and nutritional diseases and supports research, training and education for members in order to help facilitate its delivery.) and Coeliac UK. Further information can be found: www.coeliac.org.uk/healthcare-professionals/paediatrics/diagnosis-of-children

The guidance for adults suspected of having coeliac disease:

Blood testing

If someone has symptoms or is at risk of having coeliac disease the first step is to carry out a blood test. Someone with coeliac disease produces IgA antibodiesExist in the blood and are used by the immune system to attack viruses or bacteria. in response to eating glutenA protein that is found in the cereals wheat, barley and rye. . The specific IgA antibodies that are produced are endomysial antibodies (EMAEndomysial antibody - an antibody that is measured in the blood as part of the diagnosis process for coeliac disease. Depending on the laboratory performing the test, one or more antibodies may be measured (see Tissue Transglutaminase)) and tissue transglutaminase antibodies (tTGA).

It is important for patients to continue having a normal gluten containing diet before considering diagnostic tests for coeliac disease. The NICE guideline recommends that if the diet has been changed, foods that contain gluten should be eaten in at least one meal everyday for at least six weeks before testing.

The IgA tTGA and IgA EMA serological tests show high levels of sensitivity and specificity in the diagnostic process for coeliac disease.

Inaccurate blood test results

Although most negative results suggest that someone does not have coeliac disease, it is possible to have false negative results. Further investigations should be carried out in patients whose symptoms are strongly suggestive of coeliac disease.

Some research shows that patients with coeliac disease are more likely to be IgA deficientSomeone who does not produce the specific antibodies used to identify coeliac disease than the general population (2). People with IgA deficiency will have a false negative result if IgA-based serological tests are used in the diagnosis of coeliac disease.

The NICE guideline recommends using IgG antibody blood tests in those who are IgA deficient.

Biopsy

A small bowel biopsy is the gold standard for diagnosis of coeliac disease (3). Patients with a positive blood test and those with negative antibodies who are suspected to have coeliac disease should be referred to a gastroenterologistA doctor who specialises in the digestive system. .

The changes to the small bowel seen in coeliac disease are graded by Marsh classification from 0 to 4; (4)

• Marsh 0: normal mucosa
• March 1: increased number of intra-epithelial lymphocytes
• Marsh 2: crypt hyperplasia
• Marsh 3: partial or complete villous atrophy
• Marsh 4: incomplete development (hypoplasia) of the small bowel.

The diagram shows changes to the gut seen in biopsy. Clinical improvement on the gluten-freeWhen a food has less than 20 parts per million (ppm) of gluten so it is safe for people with coeliac disease to eat. diet confirms diagnosis.

Find out more information on how to review your patients with coeliac disease on the follow-up section on our website.

References

1 National Institute for Health and Care Excellence (NICE) guidelines (2009) Recognition and assessment of coeliac disease http://www.nice.org.uk/nicemedia/pdf/CG86FullGuideline.pdf

2 Lenhardt A. Plebani A. Marchetti F. et al (2004) Role of human-tissue transglutaminase IgG and anti-gliadin IgG antibodies in the diagnosis of coeliac disease in patients with selective immunoglobulin A deficiency. Digestive & Liver Disease. 36(11): 730-4

3 Abdulkarim AS & Murray JA (2003) Review article: the diagnosis of coeliac disease. Alimentary Pharmacology and Therapeutics. 17: 987-995.

4 Marsh MN (1992) Gluten, major histocompatibility complex, and the small intestine. A molecular and immunobiologic approach to the spectrum of gluten sensitivity ('celiac sprue'). Gastroenterology. 102: 330-54.