What is the relevance of genetic testing in the gluten-free world?
When a family member has been diagnosed with celiac disease, first degree relatives of those who have been diagnosed (children, parents, siblings) have a significantly higher chance of developing the condition, with prevalence ranging from 4% to 16%. In second degree relatives (uncles, aunts, nephews, nieces, grandparents, grandchildren, half siblings), the prevalence is about 2.5%.
Since these relatives have a higher chance of developing celiac disease, some may wish to find out whether they do carry the related genes. If so, then the results signal that celiac disease could potentially develop at some point in their lives. If an individual does not carry the genes, they know that it is virtually impossible for them to develop the condition in the future.
Genetic testing is applicable to celiac disease since there is a genetic component to the condition. Non-celiac gluten sensitivity (NCGS), on the other hand, is not thought to have a genetic component, although it is a condition that warrants further research. Without having the genes associated with celiac disease, it is virtually impossible to develop the condition.
Genetic testing can be especially useful to parents who have celiac disease and want to know whether their children have the potential to develop the condition. Positive genetic tests tell them that monitoring should be ongoing (see Celiac Disease Testing in Children). Negative tests would mean that no further screening is necessary.
There are two main scenarios that could warrant screening for genes associated with celiac disease:
1) If a person has stopped eating gluten before having the antibody screening tests for celiac disease. It is always advisable that testing for celiac disease be done before giving up gluten, but this does not always happen. Once a person feels better after becoming gluten-free, they are often reluctant to re-introduce gluten, so the diagnostic screening tests for celiac disease may not provide meaningful results.
2) Undergoing genetic testing for celiac disease can tell these individuals the following: If the test is positive, they know that they could have celiac disease. Since about a third of the general population carries the genes, but only one percent develops celiac disease, having the genes does not mean that celiac disease will necessarily develop. The test is more informative if it is negative: negative results tell a person that it is virtually impossible that they have, or will develop, celiac disease.
Note: The test doesn’t shed any light on whether or not a person has non-celiac gluten sensitivity (NCGS). The first step to diagnosing NCGS is generally to rule out other possible causes of symptoms, including celiac disease.