Diagnosis

People are born with a genetic predisposition to develop coeliac disease. They inherit a particular genetic make-up (HLA type) with the genes DQ2 and DQ8 being identified as the “coeliac genes”. Those with coeliac disease will have one or both of these genes. Environmental factors also play an important role in the development of coeliac disease.

Coeliac disease is not an allergy or an intolerance.

• Food allergy is the most serious form of reaction to food and can be life threatening. Allergic reactions occur when the body’s immune system overreacts to a particular substance, believing that it is harmful. Allergies are diagnosed by skin prick (or RAST) testing.
• Food intolerance (including “wheat intolerance") is not a formally defined medical term. Instead, it refers to subjective symptoms that may be related to food. A food and symptom diary in combination with a systematic and supervised elimination and challenge process may be useful in identifying food(s) that may precipitate troubling symptoms. Breath hydrogen and methane assessment can be useful to assess for fructose malabsorption or lactose intolerance.

Symptoms

The symptoms of coeliac disease vary considerably. Some people suffer severe symptoms, while others appear to be symptom free. Further investigation for coeliac disease should occur if one or more certain high risk features are present. These include:

• Iron deficiency anaemia
• Gastrointestinal symptoms
• Osteoporosis
• Autoimmune disease
• Weight loss
• Infertility
• A family history of coeliac disease.

Untreated coeliac disease can lead to chronic poor health, osteoporosis, infertility, miscarriage, depression, dental enamel defects and an increased risk of some forms of cancer.

Coeliac disease does not occur in different degrees and there is no such thing as ‘mild’ coeliac disease. All people diagnosed with coeliac disease must adhere strictly to their gluten free diet. As bowel damage may occur despite a feeling of wellness, you cannot rely on the absence of symptoms to indicate gluten tolerance.

Treatment with a strict gluten free diet allows small bowel healing and symptom resolution. Timely diagnosis of coeliac disease and treatment with a gluten free diet can prevent or reverse many of the longer term risks associated with the disease.

Diagnosis
As coeliac disease has significant health implications, a definitive diagnosis is paramount. The Coeliac Research Fund diagnostic postcard provides guidelines for diagnosis of coeliac disease. Contact your state Coeliac Society for a copy of the postcard or download a copy here.

The tests for coeliac disease are simple – just follow the steps below…

1. Keep eating gluten
Do not commence a gluten free diet prior to being tested for coeliac disease. If a gluten free diet has been adopted, the tests used to diagnose coeliac disease will be unreliable, and may be falsely negative.

If gluten has been removed from the diet, a normal diet must be resumed for at least six weeks prior to testing. During this ‘gluten challenge’, four slices of wheat based bread (or equivalent) should be consumed each day (for adults). A gluten challenge can be a daunting prospect for some people. Keep in mind that symptoms may be fairly severe for the first few days of the challenge, but they may settle with time in most people.

2. Blood Tests are used for screening
Blood tests (coeliac serology) are used to initially screen for coeliac disease. Coeliac serology measures blood antibody levels, which are typically elevated in those with untreated coeliac disease. The antibodies measured include:

• Anti-tissue transglutaminase antibodies (tTG)
• Deamidated gliadin peptide (DGP) IgA and IgG tests are now being used by a number of facilities in place of the old Anti-gliadin antibodies (AGA). The DGP IgG performs about as well as the tTG IgA. The DGP IgG can pick up individuals with coeliac disease even if they are deficient in IgA antibody and also shows particular utility in infants for detection of coeliac disease.
• Anti- endomysial antibodies (EMA). EMA is similar to tTG and is less used nowadays.

Total IgA should also be measured to exclude IgA deficiency. Approximately 2% of people with coeliac disease are IgA deficient, rendering the tTG IgA test unreliable in these people.

A diagnosis of coeliac disease SHOULD NOT be made on the basis of blood test alone. A significant level of positive coeliac blood test results may be false. If any of the coeliac serology antibody tests return a positive result, this suggests coeliac disease and warrants a biopsy of the small intestine.

In children under the age of four years the transglutaminase antibody test is less reliable. As antibody levels can fluctuate in children, it is suggested the antibody tests be performed on two occasions three months apart.

If the blood screening test returns a normal (negative) result, then coeliac disease is unlikely. However, coeliac serology only detects 85-90% of true coeliac disease. If coeliac disease is still suspected due to the presence of certain risk factors (as mentioned earlier), further investigation may be warranted.

3. A Small Bowel Biopsy is essential
A diagnosis of coeliac disease can only be made by small bowel biopsy. The optimal assessment for coeliac disease includes five biopsies taken during gastroscopy, one from the very beginning of the small intestine (the first part of the duodenum), and four further biopsies from sites scattered over the first 10-30cm of the small bowel (two biopsies from the 2nd and also the 3rd part of the duodenum). A gastroscopy is a simple day procedure done under light anaesthetic sedation that takes about 10 minutes. In the majority of cases, the bowel damage present in those with untreated coeliac disease is not visible to the naked eye. The biopsies are examined under a microscope to confirm the presence of classic small bowel changes.

It is important for patients to keep a record of the pathology report describing the microscopic changes seen by the pathologist in the small bowel biopsies. This information is helpful for doctors when assessing healing of the damage on follow up biopsy, and if there is any question about the diagnosis of coeliac disease. The report should indicate the number and quality of the biopsies received by the pathologist.

A follow up biopsy should occur at 12 – 24 months post diagnosis to confirm small bowel healing and dietary compliance. A clear follow up biopsy does not mean that you are cured. Relapse will occur if gluten is reintroduced to the diet.

Gene Testing (HLA genes)
Gene testing is presently available through pathology laboratories (by blood test or buccal (cheek) swab). People are born with the genetic predisposition to develop coeliac disease. Environmental factors then play a role in triggering the disease.

Over 99% of people affected by coeliac disease possess at least one of the genes that encode HLA DQ2 or HLA DQ8. The genes most often associated with coeliac disease are called HLA DQA1*05, and HLA DQB1*02, which together encode the HLA DQ2 protein and are often inherited together. The genes encoding HLA DQ8 are called HLA DQA1*03 and HLA DQB1*0302. The risk of coeliac disease is greater in those with the HLA DQ2 genes compared with the HLA DQ8 genes. The risk is no greater in people who have both HLA DQ2 and DQ8 than if they just had one copy of the HLA DQ2 genes.

Only one in 30 people who carry a coeliac gene will develop coeliac disease. Hence the gene test alone cannot diagnose coeliac disease. A gluten free diet should never be commenced based on a positive gene test. A gluten free diet should only be started after confirmation of coeliac disease by small bowel biopsy.

The gene test is useful for excluding coeliac disease – a negative gene test effectively rules out coeliac disease. As the gene test is not dependent on gluten intake, it can be used when people have already commenced a gluten free diet. If the gene test returns a positive result, a gluten challenge to allow diagnostic tests will be required to confirm coeliac disease.

Beware of unorthodox diagnosis techniques
There are a number of tests and treatments for allergy, intolerance and coeliac disease that are used in the absence of any scientific rationale. These tests and treatments have been shown to be unreliable when subjected to careful study. Unproven testing methods provide misleading results, delay correct diagnoses and lead to unnecessary and ineffective treatment. The Australasian Society of Clinical Immunology and Allergy (ASCIA) advise against the use of such tests for diagnosis or to guide medical treatment. Such methods may include Stool-based tests, Vega testing, Iridology, Hair Analysis or the inappropriate use of tests for Food specific Immunoglobulin. For a full list and more information about unorthodox tests and treatments, visit the ASCIA website: www.allergy.org.au.

The benefits of diagnosis
As coeliac disease is a serious medical condition with lifelong implications, a definitive diagnosis is essential.

• The only treatment currently available for coeliac disease is a strict gluten free diet. A firm diagnosis is essential before committing to this dietary regime. Adjusting to the gluten free diet may seem difficult at first. But as your knowledge and confidence grows, managing your diet becomes easier with time.
• Those who obtain a definitive coeliac disease diagnosis by small bowel biopsy are more likely to maintain their gluten free diet strictly. This has positive implications for health and management of the long term risks associated with coeliac disease.
• By obtaining a proper diagnosis, you can be assured that your symptoms are caused by coeliac disease (and should therefore improve once the gluten free diet is established) and not by another more sinister condition.
• It is likely that any potential non dietary therapy for coeliac disease, including a vaccine, will only be available to those who have biopsy proven, gene positive coeliac disease.
• As a genetic condition, there could be implications for your family once a diagnosis of coeliac disease is made. Following a diagnosis of coeliac disease, immediate family members should be screened.
• On diagnosis of coeliac disease, screening for complications and associated conditions e.g. osteoporosis or other autoimmune diseases should occur. Being diagnosed appropriately will ensure this screening takes place.
• Following proper diagnosis, a dietitian will be more likely to consider additional food intolerance if symptoms persists despite strict adherence to a gluten free diet.

Note: It is recommended that a copy of all coeliac tests including antibody, gene and biopsy tests, be kept by those diagnosed with coeliac disease.