Testing and Diagnois
Testing for Celiac Disease
Based on International Guidelines
Testing is based on antibody blood tests and biopsies from the small intestine (duodenum). A person with celiac disease produces antibodies to gluten when eaten, which can be measured. As celiac disease is an important medical condition, with lifelong implications, getting a definite diagnosis is essential.
Firstly, the person being tested should be aware that it is essential that they DO NOT stop eating gluten during the testing process. Being on a gluten-free diet can affect the results of both laboratory and endoscopic investigations. Even if laboratory investigations come back as being positive to suggest a diagnosis of celiac disease, one may still require a small intestinal biopsy to confirm the diagnosis – this is extremely important.
Adults
First choice blood test:
- Anti Tissue Transglutaminase (TTG) IgA antibodies and Total IgA levels
- (2% of people with celiac disease are IgA deficient)
- Consider Anti Endomysial (EMA) IgA antibodies if Anti TTG IgA antibodies are weakly positive. Your doctor may consider checking Anti EMA IgA antibodies
- Consider Anti EMA IgG, Anti Deaminated Gliadin Peptide (DGP) IgG and/or Anti TTG IgG antibodies if one is IgA deficient
Children (over 2 years of age)
First choice blood test:
- Anti Tissue Transglutaminase (TTG) IgA antibodies and Total IgA levels
- Consider Anti Endomysial (EMA) IgA antibodies if Anti TTG IgA antibodies are weakly positive. Your doctor may consider checking Anti EMA IgA antibodies
- Note : For Young Children (<2 years of age), consider checking both Anti TTG IgA and Anti Deaminated Gliadin Peptide (DGP) IgA antibodies as anti TTG IgA antibodies are not sensitive enough for this age group.
- For children, a biopsy may not be required in every case based on the European Society for Paediatric Gastroenterology (ESPHGAN) “Triple Test” guideline. If the child is symptomatic on eating gluten; Anti TTG IgA levels > ten times the upper limit of normal; Anti EMA IgA positive on a different blood sample. HLA-DQ2/DQ8 positive. However, this guideline is not widely accepted by all Gastroenterology Societies and recommendations to biopsy or not should be left to the evaluating physician.
Points to Note
- Anti TTG IgA is the most sensitive and specific blood test to help diagnose celiac disease in non IgA deficient individuals.
- IgA deficiency is more common in people with celiac disease, if deficient this could lead to a false negative result when testing for Anti TTG IgA
- Gluten should be eaten at least once a day for 6-8 weeks prior to testing, in order to reduce false negative testing. This gluten challenge should be discussed and monitored by your physician.
- Genetics: In order to develop Coeliac Disease HLA (human leukocyte antigen) DQ2 and/or DQ8 genes should be present. Testing can be useful to rule out coeliac disease where diagnosis is uncertain. Testing negative makes celiac disease very unlikely. However, testing positive for HLA DQ2/DQ8 cannot be used to diagnose celiac disease as the genes are found in up to 40% of people, yet only a small percentage go on to develop celiac disease.
Laboratories
Both Tan Tock Seng Hospital and Singapore General Hospital laboratories run the above mentioned tests.
Typically, private laboratories in Singapore will send these tests to one of the two above mentioned labs.
It’s important to know that if one is measuring serial antibody tests to follow up on adherence to a gluten free diet in a celiac disease patient, antibody tests should be sent to the same lab each time. This is to limit the lab variability amongst different testing kits at different hospital laboratories.
References
National Institute for Health and Care Excellence; September 2015. Coeliac disease: recognition, assessment and management
The British Society of Gastroenterology (2014) The diagnosis and management of adult coeliac disease. (panel from 8 countries)
European Society for Paediatric Gastroenterology, Hepatology & Nutrition (ESPHGAN) 2012. Guidelines for the diagnosis of coeliac disease
American College of Gastroenterology, Clinical Guidelines: Diagnosis and Management of Celiac Disease, The American Journal of Gastroenterology, Vol. 108, May 2013.
December 2017
Bridget Marr Registered Dietitian
Brian Schwender MD, FASGE, FAMS (Gastro), Senior Consultant, Gastroentetrology and Hepatology at Tucker Medical, Adjunct Assistant Professor DUKE-NUS Medical School
Disclaimer: This information was extrapolated from the above mentioned references regarding celiac (coeliac) disease. It is a guide to help you better understand how celiac disease is diagnosed. It may help you communicate more effectively with your physician. You should not use the information in this guide in place of a visit, consultation or the advice of your physician or other healthcare provider. This should not be used as the basis of self-diagnosis or treatment of celiac disease. The above mentioned authors expressly disclaim all liability for damages of any kind arising out of use, reference to, or reliance on any information provided.
