Coeliac disease: clinical features, diagnosis and management

There are several forms of gluten intolerance but not all of them are coeliac disease, a specific auto-immune response to gluten that can have a profound impact on the patient's physical health and quality of life. We discuss the diagnosis of this condition and the role of the practice nurse in its management

Gluten is a protein. It is the substance that makes dough elastic and it is found in many of the grains that form a staple part of the Western diet, including wheat, barley and rye. It is not found in corn, rice or oats, although some people feel that most oats are contaminated by other grains during milling and may therefore contain gluten.

Wheat, oats, rye and corn are all modified grasses which man has bred and grown for food for about 10,000 years. In Paleolithic times, prior to this, our hunter gatherer ancestors will have eaten plants as well as fruits and animals. However, the modified cereals (and dairy products) that form a large part of our diet today are a recent addition. It was Neolithic man, around 10,000 years ago, who began the agricultural revolution, which led to populations in the Northern hemispheres basing their diet around modified grains such as wheat. Adaptation to a gluten-based diet is therefore something relatively recent in our evolutionary history — only the last 1% of the time that man has existed on Earth.

Some dietitians have theorized that 10,000 years is insufficient for dietary adaptation through evolution — in other words gluten is a part of our diet to which we have not yet, as a species, fully adapted — and promote a 'Paleolithic' diet for health. There is, however, some disagreement about what a 'typical' diet would have been in the Paleolithic era. The proportion of the diet given to plant rather than animal products would have varied with climate and terrain. That said, Paleolithic man certainly did not eat the dairy food, modified grasses and protein food that form the main basis of the diet of many of us and our patients today. To complicate matters large numbers of people, particularly in the USA, now promote the idea of gluten-free eating as a healthier option for all.

DEFINITIONS AND CONFUSION

Coeliac disease is a specific type of gluten intolerance. The terms gluten intolerance and gluten sensitivity are interchangeable. They cover a wide spectrum of patient experiences in which gluten has an adverse effect on the body. There are two main types:

• Coeliac disease
• Non-coeliac gluten sensitivity.

Coeliac disease is a specific and diagnosable condition in which the body displays a demonstrable auto-immune response to gluten, forming antibodies to the small bowel and also, sometimes, to the skin. This leads, in the intestine, to damage to the intestinal mucosa, and, in the skin, to a rash called dermatitis herpetiformis.

Non-coeliac gluten sensitivity (NCGS) is the term for all other gluten sensitivity. Patients may have marked symptoms when they consume gluten, often of bloating and bowel disturbance, but they do not show evidence of damage to the small bowel when on a gluten-containing diet. NCGS shows considerable overlap with functional bowel disorders, including irritable bowel syndrome (IBS).

Wheat allergy is a separate condition. It is a true allergy and is usually a food allergy, although it can also occur with occupational exposure to wheat. It can cause the full range of atopic, allergic reactions including tissue swelling and angioedema, nausea and vomiting, wheezing and urticaria. It is rare, with an estimated prevalence of only 2 in 1000.¹

This article explores the diagnosis of coeliac disease specifically, and the practice nurse's role in its management.

PREVALENCE AND UNDER-DIAGNOSIS

Coeliac disease was first identified in 1888 but it was not until the 1950s that the link with gluten was understood. This link was identified through the observation that patients were cured by the deprivations of rationing in World War 2 — when access to gluten containing food was limited — but relapsed when rationing ended. The received wisdom at that time was that coeliac disease, if present, was a condition that presented in early childhood.²

In 2009 NICE produced clinical guidance on coeliac disease as it was believed that around 1% of the UK population had the condition but only 10-15% of cases had been diagnosed. The existence of an unsuspected cohort of adults with coeliac disease had been discussed in articles published in medical journals in preceding years and the NICE guideline advice was to institute investigation for coeliac disease in any adult patients with bowel symptoms or unexplained anaemia. This included all patients previously diagnosed with IBS. Indeed, a number of these patients turned out to have frank coeliac disease.¹

The prevalence of coeliac disease in mainland UK is now believed to be in the range 0.8—1.9% of adults and children. In those with an affected first degree relative the prevalence is 4.5—12%. There is some genetic basis to coeliac disease — the concordance in identical twins is about 70%.

PATHOLOGY

The jejunal villi are hair like structures from which food is absorbed. Their function is to greatly increase the absorbing area of the gut wall, and to provide enzymes 'at point of use' for digesting food. In active coeliac disease there are autoantibodies against various components of the wall of the jejunum. The jejunal mucosa becomes atrophied with the result that:

• The area for absorbing food is greatly reduced, causing malabsorption
• Food passes unchanged into the large bowel, where bacteria flourish on the sugars and starches, causing bloating and flatulence
• Transit time is quicker because the food is not being absorbed, and intestinal rush and diarrhoea are common.

Lactase, which breaks down the dairy sugar lactose, occurs in the tip of the villi. When the villi are flattened, lactase is lost, so that patients with active coeliac disease are often lactose-intolerant too.

LONG-TERM CONSEQUENCES

Delayed diagnosis of coeliac disease will result in continuing ill health and, in children, growth failure, delayed puberty and dental problems.^1,2

Studies have suggested that adults with untreated coeliac disease have a higher risk of unexplained infertility and intra-uterine growth retardation in pregnancy, osteoporosis and hip fractures. There is also possibly a slightly increased risk of non-Hodgkin's lymphoma, Hodgkin's lymphoma and small bowel lymphoma, although overall numbers are small.¹

SIGNS AND SYMPTOMS

In children and adults coeliac disease can present with a broad range of signs and symptoms. Most frequent in adults are:

• Abdominal pain/discomfort, cramping, distension
• Chronic or intermittent diarrhoea and/or steatorrhoea (fatty stools)
• Mouth ulcers and angular stomatitis, often with vitamins E, D and K deficiency
• Fatigue, with or without anaemia
• Nausea or vomiting
• Weight loss.¹

In children the most frequent presenting signs and symptoms are:

• Diarrhoea, weight loss and failure to thrive
• Vomiting, anorexia and irritability
• Protrusion of the abdomen
• Wasting of the buttocks.

Dermatitis herpetiformis is a rare condition, but when found almost all patients have active coeliac disease.

DIAGNOSIS

Whom to test

NICE have issued guidance regarding who should be tested for coeliac disease. (Table 1)

Diagnostic tests

Patients need to continue to eat gluten to enable a diagnosis to be made.

The most accurate test is endoscopic intestinal biopsy, but this is an invasive and expensive test so less selective, easier and cheaper tests are done to identify those who need biopsy.

• IgA tissue transglutaminase (tTGA) is the first choice test
• IgA endomysial antibodies (EMA) is used if tTGA is equivocal.

Serological tests are equally good in children and adults.¹

If the IgA serology is negative and the laboratory report signs suggest low IgA levels then the patient should be checked for IgA deficiency. If this is confirmed, IgG antibodies need to be measured before coeliac disease can be excluded: these are less sensitive tests in patients with normal IgA, but where IgA is reduced they are the best option.

IgA and IgG for antigliadin antibody — the old test for coeliac disease — is less accurate than either tTGA or EMA and is not now recommended.

Other tests¹

In addition to these diagnostic tests, the diagnostic work-up of suspected coeliac disease should include:

• Full blood count (FBC) — anaemia is present in 50% and iron and folate deficiency (through malabsorption) are both common
• B12, folate and ferritin
• Liver function tests (LFTs) — may show raised transaminases, which should return to normal on a gluten free diet. If they don't then the possible presence of associated autoimmune diseases which affect the liver should be considered
• Osteoporosis assessment — diet, age, activity level, BMI, previous pregnancies, sunlight exposure, other risk factors, fragility fractures.

You should also consider checking calcium and vitamin D levels as deficiencies are common.

PROBLEMS IN DIAGNOSIS

Problems may arise if the individual is not taking gluten in the diet, or if they have IgA deficiency so that levels of IgA antibodies are unusually low. Both of these situations can lead to a false negative result.

Some individuals who are already avoiding gluten will decline to return to gluten consumption in order to enable testing. These patients are difficult to diagnose and need to be referred to gastroenterology.

Patients with missed diagnosis of coeliac disease may have other diagnostic labels applied instead, particularly IBS. This may then limit further investigation.

It's important to be alert to this and, when seeing patients with a diagnosis of IBS, to remember that this is a diagnosis of exclusion and make sure that coeliac disease has been excluded.

MANAGEMENT

Management consists of excluding dietary intake of gluten. Commencement of a gluten-free diet (GFD) produces rapid symptomatic improvement and, on biopsy, the intestinal mucosa returns to normal over the same timescale.¹ There is no good evidence about what levels of gluten can be safely ingested without triggering symptoms, so affected patients should usually endeavour to avoid all gluten.^3,4

Gluten is only found in starch-containing foods, such as bread, derived from modified grasses. Fruit, meat, vegetables and fish are gluten free. The diet therefore consists of no wheat, barley or rye. Moderate quantities of oats are tolerated by most patients, although some also show sensitivity to oats. British Society of Gastroenterology (BSG) guidelines suggest oats are excluded for 12 months while patients get used to a GFD but can then be cautiously introduced. Box 1 lists sources of starch which do not contain gluten.⁵

Coeliac UK (www.coeliac.org.uk) produces a list of products that can be prescribed on the NHS, and there is a gluten-free food prescribing guide available for health professionals. The foods that can be prescribed tend to be mainly staples such as bread and pasta, rather than more 'luxury' items such as ready meals and cakes. This has been a controversial area over the years as the NHS attempts to cut prescribing costs: some argue that food costs do not belong in the NHS budget while others point out that patients with coeliac disease otherwise face an added expense through no fault of their own. Supplements such as fibre, folic acid, iron and vitamin B6, E and D are also prescribed if needed, and annual dietician and primary care review is advised.

Patient compliance with GFD is generally poor, particularly in the teenage years (this mirrors most chronic disease management). A GFD needs to be lifelong, as dietary relapse means symptom relapse.

FOLLOW-UP

Patients should have life-long follow-up.¹ We know that:

• Dietary compliance improves with regular follow-up
• Patients who do not comply with their GFD risk nutritional deficiency and reduced bone mineral density.

All patients should be reviewed annually, or sooner if there are problems. This may be in primary or secondary care, depending on the patient's condition and on local arrangements.

Practice nurses can undertake these reviews. They are in an excellent position to offer continuity and really make a difference. It may be helpful to set up a template on the software system in your surgery to make sure that everything necessary is covered.(Box 2)

REFERRAL

Specialist referral should be considered if:

• There is poor response to a GFD
• There is weight loss on a GFD
• There is blood in stools
• There is onset of unexplained abdominal pain
• There are other clinical concerns.¹

CONCLUSION

Coeliac disease has been massively under-diagnosed in the past. We formerly considered it a disease that presented almost exclusively in children as failure to thrive. In recent years we have realised that many adults with abdominal symptoms actually have coeliac disease. Many of them had quietly adapted to avoiding gluten, and many had been labelled as having IBS.

Practice nurses are well placed to detect undiagnosed coeliac disease in the practice population. This is a worthwhile task as the consequences for long term health of failure to treat can be significant.

REFERENCES

1. NICE. Recognition and Assessment of Coeliac Disease: NICE Clinical Guidance 86: May 2009: http://www.nice.org.uk/CG86

2. Steele R. Diagnosis and management of coeliac disease in children. Postgraduate Medical Journal 2011 Jan;87(1023):19-25. Epub 2010 Dec 3. http://www.ncbi.nlm.nih.gov/pubmed/21131614?dopt=Abstract

3. British Society of Gastroenterologists. Guidelines for osteoporosis in inflammatory bowel disease and coeliac disease http://www.bsg.org.uk/images/stories/clinical/ost_coe_ibd.pdf

4. Akobeng AK, Thomas AG. Tolerable amount of gluten for people with coeliac disease. Alimentary Pharmacology and Therapeutics 2008 June 1:27(11) 1044-52 http://www.ncbi.nlm.nih.gov/pubmed/18315587?ordinalpos=2&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_DefaultReportPanel.Pubmed_RVDocSum

5. British Society of Gastroenterologists. Coeliac Disease: Advice to Patients: http://www.bsg.org.uk/patients/general/coeliac-disease.html