Update on coeliac disease
Dr Sohail Butt provides essential advice to help GPs answer patients' frequently asked questions
How do you explain the difference between coeliac disease and wheat allergy?
People with coeliac disease have an intolerance to the protein gluten found in wheat, rye, barley and possibly oats. This intolerance is suggested by positive tissue transglutaminase or endomysial antibody tests, and confirmed by typical flattened mucosa found at small bowel biopsy and a positive clinical response to a gluten-free diet. Most people with coeliac disease can eat wheat once the gluten has been removed.
The diagnosis of wheat allergy is more difficult. A few people may develop quick-onset symptoms of anaphylaxis, urticaria, angio-oedema, bronchospasm or vomiting within an hour of ingestion of wheat.
However, there is a larger group of people who experience symptoms hours to days after ingestion of wheat products, whose symptoms respond to a wheat elimination diet.
Radioallergosorbent (RAST) tests, skin-prick tests, endoscopy and biopsy may offer additional clinical information, but are usually not in themselves diagnostic in this group
What are the symptoms and why has it affected the patient now?
People with coeliac disease may present with a range of symptoms and signs, and these can be divided into intestinal features and those caused by malabsorption. Many patients (especially those presenting in adulthood) have minimal or atypical symptoms, such as anaemia and chronic fatigue, and unless the diagnosis is considered the condition is easily missed or misdiagnosed in primary care.
If patients are diagnosed in their 40s, have they had the condition all their lives? Why do some patients face delay before diagnosis?
The peak age of diagnosis is 45. It is likely that most affected people have a genetic predisposition to the condition and that the illness is triggered by an as yet unidentified event and mechanism in childhood or adulthood. Studies suggest that most people have symptoms for many years prior to diagnosis, as these symptoms may be non-specific and attributed to other causes such as irritable bowel syndrome.
Is it likely to affect the patient's family?
Studies suggest that 3-5 per cent of first-degree family members of people with coeliac disease are affected by the condition. Genetic studies have identified specific HLA genes that 90 per cent of affected people will share.
If a patient has been avoiding gluten (because of symptoms caused) and requests a test for coeliac disease, how long will they have to resume eating gluten for serological tests to become positive?
The period of time needed on resuming gluten in the diet and the amount of gluten necessary to provoke serological immune response in susceptible individuals varies with each individual and is dependent on several factors. Studies suggest one factor is the amount of gluten eaten and another is the genetic predisposition of the individual.
Studies have shown that 0.3g/kg body weight/day of single gluten challenge causes immunological changes in the lining of the small intestine in paediatric patients on a gluten-free diet within two weeks.
However, other studies suggest the serological response is much slower with most patients developing a positive response in three months.
Using this evidence, many clinicians recommend eating the equivalent of about six slices of bread for at least three months prior to the serological tests.
However, if somebody experiences symptoms and feels unwell during this gluten challenge, I would consider carrying out serological tests earlier as well. If I obtained a positive test result, I would refer to hospital for an endoscopy and duodenal biopsy to confirm the diagnosis of coeliac disease.
Home test serological kits for coeliac disease are now available and are being promoted to the public. Evidence suggests these tests are as accurate as hospital laboratory tests.
Given the one in 100 positive serology rates in the general population, it is likely we will all be seeing patients requesting advice on interpretation of these results.
How should the patient be followed up?
Patients should be asked about dietary compliance and symptoms, have their height and weight checked, and blood taken for FBC, folate, alkaline phosphatase, and tissue transglutaminase antibodies. Tissue transglutaminase antibodies can be used to assess dietary compliance as they are raised in coeliac patients taking significant amounts of gluten in their diet. A review with a dietitian may be useful.
As patients have an increased risk of osteoporosis, I follow the Primary Care Society for Gastroenterology guidelines, which suggest coeliac patients should have a DEXA scan at the time of diagnosis, which is then repeated:
• at the menopause for women
• at age 55 for men
• at any age if a fragility fracture occurs.
Keeping to the gluten-free diet leads to improved bone mineral density of most coeliac patients.
Coeliac patients may have hyposplenism, which predisposes them to this serious pneumococcal infection. Hence, I follow the Department of Health advice and consider prophylatic immunisation against pneumoccocus in all my coeliac patients over two years of age.
There is an increased risk of coeliac disease in first-degree family members of
affected people, so I advise patients that
relatives should be assessed if they develop suggestive symptoms.
Are there any future developments imminent in treatment?
In recent years there has been significant progress in our understanding of the
pathological process that underlies coeliac disease.
With this knowledge comes the potential to devise therapies to block the process in susceptible individuals, which may in time lead to treatments that allow coeliac patients to ingest gluten-containing food on an occasional or regular basis.
Researchers in the Netherlands1 have tested the ingestion of specific enzymes with food, which suggests the gluten molecule may then be broken down in the stomach into harmless fragments that are not toxic to coeliac patients.
Researchers in Australia2 have further identified the exact fragments of the gluten chain that are toxic to coeliac patients. This team is now in early work on the development of a vaccine that may be used to de-sensitise people with coeliac disease.
US researchers3 have shown that people with coeliac disease may show greater permeability of the cells of the gut wall which may be mediated by the protein zonulin, and this has lead to research into zonulin receptor antagonists which may stabilise the gut membrane.
These therapies are all in the early stages of development, which may take many years to lead to safe and effective therapies. However, the progress to date seems encouraging.
Sohail Butt is a GP in Ashford, Middlesex, and a GP trainer and appraiser – he is also a member of the medical advisory committee of the charity Coeliac UK
Competing interests Dr Butt has received payment from SHS Ltd (a gluten-free food manufacturer) for acting as a primary care adviser and for attending an international symposium on coeliac disease
common symptoms of coeliac disease
• Chronic diarrhoea , weight loss and lethargy
• Diarrhoea or constipation
• Loss of appetite (short stature, osteoporosis)
• Abdominal distension
• Failure to thrive
Coeliac UK is for patients with coeliac disease and health professionals. Registered members are forwarded a pocket-sized book of gluten-free food, which includes an appendix of prescribable items. There is a section on the website with evidence-based information for healthcare professionals which may be useful to GPs.
For further information contact Coeliac UK, PO Box 220,
High Wycombe, Bucks HP11 2HY
Tel 01494 437278, fax 01494 474349 or visit www.coeliac.co.uk