Coeliac (or celiac in US) disease is an autoimmune disease – gluten triggers an immune reaction and damage to the the lining of the small intestine leading to malabsorption. The symptoms of coeliac disease vary from person to person and can range from very mild to severe. The symptoms of the disease may include:
• Diarrhoea, excessive wind, and/or constipation
• Persistent or unexplained gastrointestinal symptoms, such as nausea and vomiting
• Recurrent stomach pain, cramping or bloating
• Any combination of iron, vitamin B12 or folic acid deficiency
• Tiredness and/or headaches
• Weight loss (but not in all cases)
• Mouth ulcers
• Hair loss (alopecia)
• Skin rash (dermatitis herpetiformis (DH))
• Tooth enamel problems
• Osteoporosis/ osteopenia
• Repeated miscarriages
• Joint and/or bone pain
• Neurological (nerve) problems such as ataxia (poor muscle co-ordination) and neuropathy (numbness and tingling in the hands and feet).
In the UK there two main blood tests available to test for endomysial antibodies (EMA) and tissue transglutaminase antibodies (tTGA) which are normally produced by coeliacs when gluten is ingested. The blood tests are IgA tTGA and IgA EMA serological tests.
A small bowel biopsy is the standard method used for formal diagnosis of coeliac disease. Patients with a positive blood test and those with negative antibodies who are suspected to have coeliac disease should be referred to a gastroenterologist.
Inaccurate test results
It should be noted that for the tests to be accurate any testing for coeliac disease should be carried out whilst ingesting gluten on a daily basis for at least six weeks (there is no conclusive research as to how much gluten needs to be consumed to produce accurate results).
Although most negative results suggest that someone does not have coeliac disease it is possible to have false negative results. Further investigations should be carried out in patients whose symptoms are strongly suggestive of coeliac disease.
Some research shows that patients with coeliac disease are more likely to be IgA deficient than the general population. People with IgA deficiency will have a false negative result if IgA-based serological tests are used in the diagnosis of coeliac disease.
The identification of two human leukocyte antigen molecules in people with coeliac disease, HLA-DQ2 and HLA-DQ8, provides further information on who may develop coeliac disease. About 90% of individuals with coeliac disease will carry the DQ2 gene and most of the remaining individuals will carry the DQ8 gene. These HLA genes are associated with approximately 40% of the heritable risk of developing coeliac disease.
Testing of these genes can not be used to diagnose coeliac disease as these genes are also present in people without coeliac disease. It is unlikely that someone would have coeliac disease if they do not have these genes.
Comment on diagnosis
On the path to diagnosis many patients are mis-diagnosed with various illnesses and disorders such as; irritable bowel syndrome (which is no diagnosis at all really), ME, ‘viruses’, ‘runner’s tummy’ etc. The average age of diagnosis of coeliac disease is 40. This is quite startling when many people will have been suffering for over 20 years.
Where a patient strongly suspects they have an issue with gluten they are advised not to discontinue eating gluten containing products. It seems counter-intuitive to do this and many patients will rather cut out gluten and feel well than go through an often protracted diagnostic process.
It is unusual that for a serious condition in order to accurately test for a disease the patient needs to actively consume the item that makes them ill for six weeks. In circumstances where a person is too ill to go through with diagnosis, or feels unable to consume gluten for six weeks, a firm diagnosis of coeliac disease will not be made.