Coeliac disease screening and diagnosis

Coeliac disease is a common autoimmune condition characterised by an exaggerated immunological response to ingested gluten. The only treatment for coeliac disease is strict adherence to a life-long, gluten free diet. However, left undiagnosed and/or untreated, coeliac disease can have negative health implications, including an increased risk of lymphoma, osteoporosis, hyposplenism, anaemia, and other micronutrient deficiencies. Therefore, it is important that children and adults who experience symptoms commonly associated with coeliac disease, be screened for this condition. 

It is recommended that coeliac disease be screened for in people with any of the following:

• persistent unexplained abdominal or gastrointestinal symptoms
• faltering growth
• prolonged fatigue
• unexpected weight loss
• severe or persistent mouth ulcers
• unexplained iron, vitamin B12 or folate deficiency
• type 1 diabetes, at diagnosis
• autoimmune thyroid disease, at diagnosis
• irritable bowel syndrome (in adults)
• first-degree relatives of people with coeliac disease.

Screening for coeliac disease may also be considered in people with any of the following:

• metabolic bone disorder (reduced bone mineral density or osteomalacia
• unexplained neurological symptoms (particularly peripheral neuropathy or ataxia)
• unexplained subfertility or recurrent miscarriage
• persistently raised liver enzymes with unknown cause
• dental enamel defects
• Down's syndrome
• Turner syndrome

An important point here is that coeliac screening should occur before a diagnosis of IBS is made.

How is coeliac disease diagnosed?

There are a number of blood tests that can be used to screen for coeliac disease. These screening bloods tests either look for antibodies a person with coeliac disease produces when they’re exposed to gluten or for genes associated with coeliac disease. The type of screening blood test you undergo should be determined by your gluten intake.  If you are following a gluten-containing diet, a diagnosis of coeliac disease can be made using antibody tests followed by a duodenal biopsy. However, if you are following a gluten free diet, these test may provide a false negative result.

People following a gluten free diet can also be screened for coeliac disease using a genotype test. This test is accurate even in people following a gluten free diet, although it is only a screening test and cannot be used to diagnose coeliac disease. This means that if you get a positive result to the genotype test, you still need to undergo a duodenal biopsy to confirm the presence of coeliac disease. By contrast, a negative result is highly predictive for the absence of coeliac disease and usually, no further screening tests will be required.

A duodenal biopsy is regarded as the gold standard method for diagnosing coeliac disease. This test looks for the presence of villous atrophy and increased intraepithelial lymphocytes. However, to ensure an accurate result, it is very important that you are following a gluten containing diet in the weeks preceding your biopsy. 

What is a gluten challenge?

A gluten challenge is a period during which gluten is reintroduced to the diet of someone who is otherwise following a gluten free diet. A gluten challenge is used to induce changes in antibody levels and/or the small intestinal mucosa necessary to diagnose coeliac disease. Ideally, the gluten challenge should consist of daily ingestion of ≥3 g gluten (equivalent to 2 slices of bread) over 6-8 weeks to induce adequate changes in antibody and mucosal markers of coeliac disease.

Are there other tests that may be used to diagnose coeliac disease?

There are many tests for coeliac disease that can be purchased online and completed at home. However, despite marketing claims, results from these tests are unreliable and they should not be used to diagnose this condition. Examples of unreliable tests for coeliac disease include:

• Applied kinesiology
• Hair analysis
• IgG gliadin antibody tests
• Leukocytoxic tests
• Vega testing

If you suspect you may have coeliac disease, it is very important that you talk to your doctor and undergo the appropriate testing.

Take-home messages

1. If you have IBS or IBS-like symptoms, but have never been screened for coeliac disease, talk to your doctor about having the appropriate coeliac screening tests.
2. If you are referred for an antibody test or a duodenal biopsy, make sure you are including sufficient gluten in your diet in the 6-8 weeks preceding these tests.
3. The genetic and antibody tests screen for coeliac disease, but do not diagnose the condition – a duodenal biopsy is the most reliable method of diagnosing coeliac disease.
4. If you are diagnosed with coeliac disease, let you family members know and encourage them to also be screened for coeliac disease (risk of coeliac disease is much higher in people with a first-degree relative with coeliac disease).
5. If you are diagnosed with coeliac disease, see an expert dietitian for advice on implementing a gluten-free diet and for assessment of adherence if your symptoms persist

References:

1. Mooney PD, Hadjivassiliou M, Sanders DS. Coeliac disease. Bmj. 2014;348:g1561.
2. Internal Clinical Guidelines T. National Institute for Health and Care Excellence: Clinical Guidelines. Coeliac Disease: Recognition, Assessment and Management. London: National Institute for Health and Care Excellence (UK)
3. Leffler D, Schuppan D, Pallav K, et al. Kinetics of the histological, serological and symptomatic responses to gluten challenge in adults with coeliac disease. Gut 2013;62:996-1004