Gluten sensitivity screening

What is gluten sensitivity screening?

Gluten sensitivity screening usually means a blood test that looks for antibodies your body may produce in response to gluten, to help find out whether you have coeliac disease.

It's different from testing for non-coeliac gluten sensitivity, sometimes called gluten intolerance, which currently has no specific blood test and is instead diagnosed by a process of elimination.

Why might I need gluten sensitivity screening?

You might be offered this screening if you have symptoms such as:

• diarrhoea, bloating, wind or stomach pain
• persistent tiredness (fatigue)
• unexplained weight loss
• severe or persistent mouth ulcers
• anaemia, or a lack of iron, vitamin B12 or folate that isn't otherwise explained.

You might also be tested if you have a close relative with coeliac disease, or if you have a related condition such as type 1 diabetes or an autoimmune thyroid disease.

What are the benefits of gluten sensitivity screening?

Finding out early whether coeliac disease is the cause of your symptoms means you can start a gluten-free diet sooner, which can ease your symptoms and reduce the risk of complications, such as weak bones, developing later.

If your test is negative, it can also help rule coeliac disease out, so you and your doctor can look at other possible causes.

Are there different types of gluten sensitivity screening?

• Tissue transglutaminase (tTG-IgA) test: The usual first test, which looks for the most common antibody linked to coeliac disease
• Additional antibody tests, such as endomysial antibodies (EMA) or deamidated gliadin peptide (DGP) tests: These may be used if your first result is unclear, or if you have low levels of IgA, a separate antibody the main test depends on.

If your blood test suggests coeliac disease, you may then need a biopsy of your small intestine to confirm the diagnosis.

If you don't have coeliac disease but still have symptoms after eating gluten, this may be non-coeliac gluten sensitivity, which is diagnosed differently, through an elimination diet, since there's currently no specific test for it.

How do I prepare for gluten sensitivity screening?

• Keep eating gluten-containing foods: Before and during the testing process. Cutting out gluten or reducing how much you eat can affect the accuracy of your results.
• Don't start a gluten-free diet before testing: Or before a diagnosis has been confirmed, even if you think gluten is causing your symptoms.
• If you're already following a gluten-free diet: Your doctor may recommend a gluten challenge before testing. This involves eating gluten again for a period of time so that coeliac disease-related antibodies can build up and be detected. The amount and duration vary depending on your individual circumstances, so this should only be done under the guidance of a healthcare professional. If you are pregnant, speak to your healthcare professional before making any dietary changes or undertaking a gluten challenge.
• Consider keeping a food and symptom diary: Recording what you eat and any symptoms you experience can help your doctor assess whether your symptoms may be related to gluten and support the diagnostic process.

What happens during gluten sensitivity screening?

1. A healthcare professional takes a sample of blood, usually from a vein in your arm
2. The sample is sent to a laboratory and checked for antibodies linked to coeliac disease
3. If your antibody test is positive, or if your symptoms strongly suggest coeliac disease despite a negative test result, you will be referred to a gastroenterologist (a doctor who specialises in conditions affecting the digestive system) for further assessment
4. The specialist may arrange further blood tests, or a biopsy of your small intestine to confirm the diagnosis
5. For the biopsy, a thin, flexible tube with a camera (an endoscope) is passed through your mouth and down to your small intestine, usually after a local anaesthetic to numb your throat and sometimes a sedative to help you relax
6. Small samples of the lining of your small intestine are taken through the endoscope and examined under a microscope.

What happens after gluten sensitivity screening?

Your GP or specialist will explain what your blood test results mean. If coeliac disease is confirmed, you shouldn't start a gluten-free diet until this is done, even if an earlier blood test was positive.

You may have further blood tests to check your levels of iron and other vitamins and minerals, since coeliac disease can affect how well your body absorbs nutrients. A bone density scan (DEXA scan) may also be recommended if your doctor thinks the condition may have affected your bones.

If you were assessed for non-coeliac gluten sensitivity instead, your doctor may suggest removing gluten from your diet for a period and then reintroducing it, to see whether your symptoms improve or return.

What are the risks of gluten sensitivity screening?

• The test may miss coeliac disease (a false negative result): This can happen if you've reduced or stopped eating gluten before the test, or if you have a condition called IgA deficiency, which can make the main antibody test less reliable.
• The test may suggest coeliac disease when it isn't present (a false positive result): This is uncommon but can occur in people with certain other autoimmune conditions.
• Inconclusive antibody result: Sometimes the antibody test does not provide a definite answer. If this happens, your doctor may recommend additional blood tests or a biopsy.
• You may need further tests: A positive antibody test alone is not always enough to confirm coeliac disease. Some people will need an intestinal biopsy or other investigations, and your specialist will explain the benefits and risks of any additional procedures.
• Waiting for a diagnosis can be frustrating: It is important to keep eating gluten until all recommended tests have been completed, even if you think gluten is causing your symptoms, as stopping too soon can affect the accuracy of the results.