It is important that if you think you might have coeliac disease to first talk to your doctor.
If you suspect you have coeliac disease you need to stay on a normal gluten-containing diet - a gluten free diet should not be started as it will interfere with establishing the correct diagnosis. A diagnosis cannot be made simply by you trialing a gluten free diet and feeling better/symptom free. If a gluten free diet has already been adopted, the tests used to diagnose coeliac disease are unreliable, and can be falsely negative. (See Already gluten free? below)
When visiting your GP you should mention if a relative has coeliac disease and/or dermatitis herpetiformis, or if you or a family member has been treated for anaemia.
Blood tests (coeliac serology) are used to screen for coeliac disease. ‘Coeliac serology’ measures antibody levels in the blood which are typically elevated in people with untreated coeliac disease.
This involves a gastroscopy procedure in which several tiny samples (biopsies) of the small bowel are taken. 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 villous atrophy.
Gene (HLA) testing is a useful in cases when the diagnosis of coeliac disease is not certain. This can occur if the blood or small bowel biopsy results are difficult to interpret, or if adequate gluten was not being consumed to make the test reliable. It requires a simple blood test. Over 99% of people affected by coeliac disease possess either HLA DQ2, HLA DQ8, or parts of these genes. However, the gene test alone cannot diagnose coeliac disease as not everyone with the gene will develop coeliac disease.
If you have a negative result to the gene test, it effectively rules out a diagnosis of coeliac disease.
The gene test does not rely on a person eating gluten so can be used when people have already commenced a gluten free diet. If the gene test is negative for HLA DQ2 and HLA DQ8 then coeliac disease can be ruled out. If the gene test is positive for HLA DQ2 or HLA DQ8, then a gluten challenge followed by small bowel biopsy will be required to correctly diagnose coeliac disease.
Already gluten free?
If gluten has been removed from the diet, a normal diet must be resumed for four to eight weeks prior to testing (please check with your GP or specialist). During this ‘gluten challenge’, a minimum of four slices of wheat based bread (or equivalent) should be consumed each day (for adults) (2 slices of wheat based bread each day for children). It is important the gluten challenge is carried out properly to ensure reliable testing results.
You are not alone! Get support, further your knowledge and understanding, and learn to live a full life by becoming a member of Coeliac New Zealand. The organisation is made up of people of all ages who have had similar experiences to you.
Tell your doctor about our Health Professional Memberships
Coeliac New Zealand is here to support health professionals with information and resources as they guide patients through their coeliac disease diagnosis and assist them in managing their gluten free diet. We offer two types of memberships for health professionals - those in the public and those in the private sector. For health professionals in the public sector, their membership is free. Check our health professional section to find out more.
You can tell your doctor about these memberships by passing on our Health Professional flyers.