Diagnosing Coeliac Disease - Best Practice
Coeliac disease cannot be diagnosed based on symptoms alone. The symptoms are so varied, can occur at any age and can often mimic those of other diseases. A gluten free diet should never be trialled before testing for coeliac disease.
Gold standard diagnosis
The current best practice pathway to diagnosis is:
Blood or serology tests
Blood or serology tests are used for initial screening (“coeliac serology and IgA”). People taking this test must be consuming gluten prior to and at the time of testing. If gluten has been removed prior to testing a gluten challenge will be required. A gluten challenge involves eating the equivalent of four slices of wheat based bread per day (for adults) for six weeks prior to testing.
If the results of the test are positive (or if they are negative, but the doctor is still concerned that coeliac disease may be present) a referral to a gastroenterologist is necessary to confirm that the lining of the small bowel has been damaged by coeliac disease.
Gastroscopy
If the blood test is positive, or if coeliac disease is still suspected after a negative blood test result, a gastroscopy must be carried out to confirm the initial diagnosis. In this procedure, an endoscope is passed through the mouth into the small bowel to take tiny samples (biopsies) which will show if gluten is causing damage.
A gastroscopy is performed in a hospital or day-procedure centre under sedation and most people find it a very straightforward procedure with no discomfort.
Taking a biopsy from the small bowel is an essential part of diagnosing coeliac disease because a blood test alone is not definitive.
If the biospy is positive and the person starts a gluten free diet, a follow up biopsy 12-24 months post diagnosis is recommended to assess compliance and bowel repair.
Gene Test
In the last few years a gene test (also known as the ‘HLA gene test’) has been available. This is useful in determining a person’s risk of coeliac disease. Two genes are associated with coeliac disease - HLA DQ2 and HLA DQ8. It is throught that 99.6% of all people with coeliac disease have at least one of these two genes. Having the genes gives a person the pre-disposition to coeliac disease, the genes do not cause coeliac disease. It is important to stress that only 1 in 30 people with either of these genes will develop or have coeliac disease.
The testing for the two genes can be done by a simple blood test or by taking a scrape from the inside of the cheek which provides DNA - known as a buccal scrape.
The gene test does not depend on a gluten challenge therefore it can be useful in assessing those on a gluten free diet or those on reduced gluten intake. If the gene test is negative, then it is unlikely a person has coeliac disease. If the gene test is positive, then further tests whilst following a gluten challenge will need to be performed.
Self diagnosis
It is important to understand that trialling a gluten free diet cannot provide a correct diagnosis of coeliac disease.
Furthermore, medical investigations while a person is on a gluten free diet may produce negative results and may delay the diagnosis of coeliac disease or another condition with similar symptoms. This includes both the serological testing [blood tests] and histological testing [biopsy].
Self diagnosis and elimination of gluten from one’s diet without medical advice is dangerous. Coeliac disease is a serious condition which requires medical diagnosis and treatment.
Click here for Dr Jason Tye-Din’s article on making sense of your diagnosis
Details of the correct diagnosis pathway can be obtained from our easy to follow guide.
The Coeliac Research Fund has developed an information CD on diagnosing Coeliac disease – to obtain a copy, please telephone 1300 990 273 or email info@coeliacresearchfund.org