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Coeliac disease: a guide to diagnosis and management

Nicky Mendoza
BSc SRD
Dietitian
Coeliac UK
E:n.mendoza@coeliac.co.uk

Coeliac disease is caused by intolerance to gluten leading to inflammation and damage to the gut. The villi become flattened (see Figures 1 and 2), which greatly decreases their surface area, and hence absorption of nutrients, and can lead to nutritional deficiencies and even malnutrition. In fact, coeliac disease is the most common cause of malnutrition in the UK.(1) Coeliac disease is a genetic autoimmune disease, with the likelihood of being passed on to a first-degree relative of 1 in 10.(2,3)

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Coeliac disease is not the same as other food intolerances as an actual disease process occurs, which can lead to serious complications such as osteoporosis, bowel cancer and infertility. The disease remains vastly underdiagnosed. Coeliac UK believes that, of the 750,000 people with the disease, 500,000 remain undiagnosed.

Symptoms and diagnosis
The most common age of diagnosis of coeliac disease is 50 years; many people are therefore undiagnosed for several decades.(4)
The "classic" symptoms are diarrhoea and weight loss, but many patients present with symptoms that would not normally be connected with food intolerance, which is one reason why coeliac disease remains so underdiagnosed (see Table 1). Children often present with the disease following weaning onto gluten-containing foods with symptoms such as pale loose stools, ­bloating, failure to thrive and general unhappy behaviour. In older children, stunting and anaemia are also seen. Symptoms in adults are more diverse, and irritable bowel syndrome (IBS) is a common misdiagnosis due to the similarity of symptoms.(5) Lethargy and anaemia, common to coeliac disease, can also be put down to other reasons, and therefore diagnosis is often not considered.

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There is a clear diagnostic procedure for coeliac disease. The first step, a blood test, can be carried out by anyone trained to take blood. The test looks for antibodies that are produced in response to gluten, namely endomysial antibodies (EMAs) and tissue transglutaminase antibodies (tTGAs). This blood test is 90-95% accurate. To confirm diagnosis it is necessary that the second step, an intestinal biopsy, is performed to check for the characteristic changes in the gut lining. A patient who has symptoms suggestive of coeliac disease should be referred for biopsy regardless of antibody results, as not all coeliacs produce the antibodies that are tested for. The biopsy is still considered to be the gold standard for diagnosis.(6)
To avoid obtaining a false-negative result, both tests require that the patient is on a diet containing gluten. If a patient has stopped eating gluten they should reintroduce it for at least six weeks before being tested.(7) People are often unwilling to go back onto a diet that they know will make them feel unwell, so it essential that tests are performed before a gluten-free diet is suggested.

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Treatment and management
Treatment for coeliac disease is adoption of a gluten-free diet, which must be adhered to for life. As well as avoiding obvious gluten-containing foods, such as bread, pasta, breakfast cereals, pastry, cakes and biscuits, adhering to a gluten-free diet also means avoiding foods that contain hidden gluten. Wheat starch is used as an ingredient in many foods and also in some medications. It is therefore important to check the gluten status of medications before prescribing them for patients with coeliac disease.
There is a growing range of gluten-free alternatives on the market. Staples such as bread, pasta, plain biscuits and crackers, pizza bases and flours are available on prescription, while gluten-free ranges in supermarkets and health food shops also include "luxury" items. The cost of gluten-free foods is high as it is a niche market, so many coeliacs prefer to get their gluten-free staples on prescription. Research has shown that prescriptions improve compliance with the diet, and thus ensuring that a patient is provided with correct amounts of gluten-free foods on prescription is an essential part of their treatment.(8)
Adherence to a gluten-free diet reduces the risk of complications such as gut cancer and osteoporosis.(9) For coeliacs who are diagnosed later in life, it is important that the increased risk of osteoporosis, due to long-term malabsorption of calcium, is taken into account and the patient is referred for a DEXA scan and then followed up on a regular basis.

Recent developments
The prevalence of coeliac disease is much higher than previously thought, with the incidence being at least 1 in 100. This suggests that, in a general practice with 5,000 patients registered, approximately 50 will have coeliac disease. Many of these patients may have been misdiagnosed as having IBS, while others may undergo tests for symptoms such as TATT (tired all the time), with coeliac disease not even being considered as a possibility.
There is an increased incidence of coeliac disease in people who have other autoimmune diseases, such as type 1 diabetes and hypothyroidism.)(10) It has been suggested that children with type 1 diabetes should be screened for coeliac disease, as the presentation is often silent.(11) Recent research has found that diabetes control often improves following the diagnosis of coeliac disease and introduction of a gluten-free diet.(12) However, as absorption of nutrients improves, an increased dose of insulin may be required to counterbalance the possible rise of blood glucose.

Prescribing guidelines
There is now a set of guidelines outlining reasonable amounts of gluten-free food that a coeliac patient should receive on prescription, which are based on nutritional requirements and take into account age and sex.(13) These guidelines are aimed at helping healthcare professionals prescribe an adequate amount of gluten-free foods that a patient with coeliac disease would require on a monthly basis (see Tables 2 and 3). Conditions such as pregnancy and breastfeeding are taken into account, as well as levels of activity. These guidelines should be used as guide only, and for individual advice on the amounts required patients should be referred to a dietitian. Despite these guidelines, many GPs do not prescribe adequate amounts of gluten-free products.

Labelling
Changes to the EU labelling directive (Directive 2003/89/EC) will remove the 25% compound ingredient rule and will mean that all allergens contained in food will have to be listed in an allergen advice box. This new legislation is currently being incorporated into UK law and will be obligatory by 25 November 2005. Gluten is included in the list of allergens, which also covers shellfish, eggs, fish, peanuts, soya beans, milk and dairy produce, nuts, celery, mustard, sesame seeds, sulphur dioxide and sulphites. The new labelling rules will make gluten-containing foods easily identifiable, so coeliacs will be able to shop more efficiently and without feeling unsafe.

Conclusion
With one in 100 of the population suffering from coeliac disease and with the possibility of serious complications that are costly to treat, this is a condition that should be considered in patients presenting with a range of symptoms and not just the patients presenting with the "classic" symptoms of diarrhoea and weight loss. The gluten-free diet provides a complete treatment, which both eliminates symptoms and reduces the risk of complications.

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References

  1. Thomas PD, Forbes A, Green J, Howdle P. Guidelines for the ­investigation of chronic diarrhoea.Gut 2003;52 Suppl v:v1-v15.
  2. Bingley PJ, Williams AJ, Norcross AJ, et al. Avon longitudinal study of parents and children study team.BMJ 2004;328:322-3.
  3. Hogberg L, Grodzinsky E, Stenhammer L. Familial prevalence of coeliac disease: a twenty year follow-up study. Scand J Gastroenterol 2003;38(1):61-5.
  4. Hin H, Bird G, Fisher P, Mahy N, Jewell D. Coeliac disease in primary care: case finding study. BMJ 1999;318:164-7.
  5. Shahbazkhani B, Forootan M, Merat S, et al. Coeliac disease presenting with symptoms of irritable bowel syndrome. Aliment Pharmacol Ther 2003;18:231-5.
  6. Anonymous. Revised criteria for diagnosis of coeliac disease. Arch Dis Childhood 1990;65:810-11.
  7. Berger A. Coeliac disease specific antigen found. BMJ 2000;320:736.
  8. Coeliac UK and Nutricia Healthcare. Project Harvest. London:?Coeliac UK; 2001.
  9. Green PH, Jabri B. Coeliac disease. Lancet 2003;362(9381):383-91.
  10. Buysschaert M. Coeliac disease in patients with type 1 diabetes mellitus and auto-immune thyroid disorders. Acta Gastroenterol Belg 2003;66(3):237-40.
  11. Holmes GK. Screening for coeliac disease in type 1 diabetes. Arch Dis Childhood 2002;87:495-8.
  12. Saadah OI, Zacharin M, O'Callaghan A, Oliver MR, Catto-Smith AG. Effect of gluten-free diet and adherence on growth and diabetic control in diabetics with coeliac disease. Arch Dis Childhood 2004;89:871-6.
  13. Holmes GK. Gluten-free foods:a prescribing guide. London: Good Relations Healthcare; 2004.

Resources
Coeliac UK
Helpline:0870 4448804
W:www.coeliac.co.uk