Blood tests for IBS

A simple and minimally invasive way to diagnose and monitor problems within the body is by performing tests on a sample of your blood.

There are a whole host of markers than can be examined, that can give a clear picture of what is going on inside. Some tests look for chronic inflammation and others look for specific diseases such as coeliac disease.

We outline here some of the tests we do frequently. The actual tests you need will depend on your symptoms, so you need to see the right doctor to make sure you get the right tests.

Tests that may be done, depending on your symptoms include:

  • Coeliac disease: Coeliac disease is an autoimmune disease affecting the small intestine, triggered by certain proteins found in wheat. It can cause many of the same symptoms as IBS, including diarrhoea, weight loss and abdominal pain/bloating. If your Coeliac test comes back positive, then you will be advised on how to control the disease by factors such as diet and vitamin supplements. The standard blood tests for this disease are anti-endomysial antibody and tissue transglutaminase. Results are usually available in a few days. Interpretation is not always straightforward and may need an expert to get the correct diagnosis.
  • Specific Immunoglobulin A (IgA) Deficiency: Patients suffering with IgA deficiency are lacking the ability to produce a certain type of antibody that helps protect specifically against gut infections. As a result, they are particularly prone to infections of the digestive tract which can lead to abdominal symptoms similar to IBS. There is currently no known cure for IgA deficiency; however patients whose blood tests are positive for the condition are closely monitored so that infections can be treated early. People who have specific IgA deficiency will probably have a false negative test for coeliac disease.
  • Thyroid disorders: Your thyroid gland is responsible for secreting hormones that have a wide range of functions throughout the body. A simple blood test can check for levels of these hormones, and allow doctors to check whether your thyroid is underactive or overactive. Either of these conditions can lead to symptoms similar to IBS. An underactive thyroid tends to cause constipation. An overactive one tends to cause diarrhoea, although curiously, sometimes people with an underactive thyroid also appear to get diarrhoea. If your blood test is positive for a thyroid disorder, your doctor can prescribe treatments to restore normal function. This should improve your symptoms. If you are already on thyroid replacement therapy for an underactive thyroid, it is still important to check your thyroid levels as the wrong dose of replacement can lead to worsening of bowel symptoms.
  • Inflammatory markers: One of the key causes of gut symptoms is chronic inflammation within the digestive tract. By observing levels of these markers in the blood, your doctors can have a general picture of inflammation in the body, although the tests don’t necessarily pinpoint where or why this inflammation is going on. If you test positive for inflammatory markers such as CRP or ESR, it could be an indication of active infection, or inflammatory bowel disease, and you will more than likely be sent for further testing to investigate the source/cause of the positive test.

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