Coeliac disease can be diagnosed at any age, and presents in both children and adults.
Delayed diagnosis of coeliac disease is common. Research shows the average time it takes to be diagnosed is 13 years.
Most people with coeliac disease have antibodies that show up in their blood. The first stage in diagnosis can be a blood test.
Who'll have a blood test
A blood test should be offered if you've any of the following:
- type 1 diabetes
- autoimmune thyroid disease
- dermatitis herpetiformis
- irritable bowel syndrome (IBS)
- anaemia without an obvious cause
- certain symptoms related to your digestive system – such as frequent diarrhoea, abdominal pain or vomiting, nausea or sudden weight loss
- close relatives (parents or siblings) with coeliac disease
A blood test might also be offered if:
- you feel tired all the time
- a child is not growing as fast as expected
- you've other symptoms or conditions that sometimes occur in people with coeliac disease – such as mouth ulcers, particular types of problems with your bones or liver, Down's syndrome, Turner syndrome or persistent constipation
Blood tests for coeliac disease are not recommended for infants who've not started to eat foods containing gluten.
Before a blood test
Before a blood test is given, it's important that the patient eats gluten-containing foods in more than one meal every day for at least 6 weeks before the test.
What's involved in a blood test?
A blood test for coeliac disease involves taking a blood sample and testing it for antibodies in the blood.
For the test to be successful, a person must have been eating gluten-containing food in more than 1 meal for at least 6 weeks before the test.
Blood tests are 95% accurate at diagnosing coeliac disease.
If coeliac disease antibodies are found in your blood, your GP will refer you for a biopsy of your gut.
It's sometimes possible to have coeliac disease and not have antibodies in your blood.
If you continue to have coeliac disease-like symptoms, despite having a negative blood test, your GP may still refer you for a biopsy of your gut.
A biopsy can help confirm a diagnosis of coeliac disease.
If you're referred for a biopsy, this will be carried out in hospital and usually by a doctor that specialises in treating conditions of the stomach and intestines called a gastroenterologist.
What's involved in a biopsy?
If you need to have a biopsy, a thin flexible tube with a light called an endoscope will be inserted into your mouth and passed down to your small intestine.
Before the procedure, a local anaesthetic is given to numb the throat and/or a sedative to help you relax.
During the procedure, the doctor will pass a tiny biopsy tool through the endoscope to take samples of the lining of your small intestine. The sample will then be examined under a microscope for signs of coeliac disease.
Diet before and after testing
It's very important that people continue to eat gluten-containing foods every day until a diagnosis has been confirmed.
A biopsy will only show coeliac disease if the person being tested has been eating gluten-containing foods regularly.
Only after coeliac disease is confirmed can the patient start a gluten-free diet.
If you're already on a gluten-free diet and find it hard to reintroduce gluten, your GP should refer you to a specialist and explain to you that you may not be able to get gluten-free foods on prescription if you don't have your coeliac disease confirmed by biopsy.
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Tests after diagnosis
If you've been diagnosed with coeliac disease, you may also have other tests to assess how the condition has affected you so far.
Additional blood tests
You may have further blood tests to check levels of iron and other vitamins and minerals in your blood. This will help determine whether the poor absorption of food from your gut caused by the coeliac disease has led to you developing anaemia (a lack of iron in your blood).
Dual energy X-ray (DEXA) scan
In coeliac disease, a lack of nutrients caused by poor absorption can make bones weak and brittle (osteoporosis).
A DEXA scan is a type of very low dose X-ray that measures bone density. This may be required if your GP or consultant thinks that your condition may have started to affect your bones.
You can now buy over-the-counter tests for coeliac disease at pharmacies. There isn't enough evidence that these tests are reliable.
If you've used one, it's important that you talk to your GP about the result.
Before a diagnosis can be confirmed, you'll still need to have a blood test and biopsy.