Coeliac & Gastrointestinal Testing

Investigating Coeliac Disease and Gastrointestinal Symptoms

Persistent bloating, diarrhoea, abdominal discomfort, unexplained nutritional deficiencies and other gastrointestinal symptoms can have many possible causes. Blood testing can help investigate selected conditions, including Coeliac Disease, and can identify abnormalities that may provide clues about nutritional absorption, inflammation or wider health.

YT Medical offers targeted Coeliac & Gastrointestinal Blood Testing according to the symptoms and clinical question being investigated. Blood tests are useful, but many gastrointestinal conditions cannot be diagnosed from blood alone, and further investigation may sometimes require stool testing, breath tests, imaging, endoscopy or specialist gastroenterology assessment.

Which Coeliac Blood Tests Are Available?

The principal blood test used when investigating Coeliac Disease is IgA Tissue Transglutaminase Antibody (tTG-IgA) together with measurement of Total IgA.

Coeliac Disease is an autoimmune condition in which gluten triggers an immune reaction that damages the lining of the small intestine. tTG-IgA provides an effective first-line serological screen in most patients.

Total IgA is important because some people are deficient in IgA. In these patients, a standard IgA-based coeliac test can give a misleading negative result. Where IgA deficiency is present, IgG-based testing such as IgG tTG, IgG Endomysial Antibody or Deamidated Gliadin Peptide antibodies may be considered.

Endomysial Antibody (EMA) testing may also be used to help clarify or confirm selected positive or borderline serology.

Do Not Stop Gluten Before Testing

For coeliac blood testing to be reliable, the patient needs to be eating gluten before and during the diagnostic process.

Current guidance recommends including gluten in more than one meal each day for at least six weeks before testing. Starting a gluten-free diet before the blood test can reduce antibody levels and potentially produce an inaccurate negative result.

If a patient has already substantially reduced or eliminated gluten, this should be discussed before testing rather than simply proceeding with a standard coeliac screen.

A positive blood test does not always represent the final diagnosis. Gastroenterology referral and additional investigation may be required, and patients should not begin a permanent gluten-free diet until the diagnostic process has been appropriately completed.

Wider Gastrointestinal Blood Tests

Depending on the symptoms present, additional blood tests may include a Full Blood Count, Ferritin and Iron Studies, Vitamin B12, Folate, Vitamin D, Liver Function and inflammatory markers such as C-Reactive Protein (CRP).

These tests do not diagnose most gastrointestinal conditions directly, but they may identify consequences or associated abnormalities. Coeliac Disease, for example, can be associated with iron, folate, B12 and vitamin D deficiency where nutrient absorption has been affected.

A Full Blood Count may identify anaemia or other blood-cell abnormalities, while CRP can provide information about systemic inflammation. A normal inflammatory marker does not, however, exclude all gastrointestinal disease.

Some Gastrointestinal Tests Are Not Blood Tests

A comprehensive gastrointestinal investigation may sometimes require tests beyond venous blood sampling.

Faecal calprotectin, for example, is measured in a stool sample and can help differentiate inflammatory bowel disease from some non-inflammatory gastrointestinal conditions. H. pylori infection may also be investigated using a stool antigen test or urea breath test depending on the clinical circumstances.

Persistent bowel symptoms should therefore not be assumed to have been fully investigated simply because a blood panel is normal.

When Further Assessment Is Needed

Symptoms including unexplained gastrointestinal bleeding, black stools, persistent vomiting, progressive difficulty swallowing, significant unexplained weight loss or a substantial persistent change in bowel habit may require timely medical assessment.

Likewise, positive coeliac serology or evidence of significant anaemia or nutritional deficiency may warrant further investigation through a GP or Gastroenterology service.