10 Must Know Facts about 23andme celiac disease genetic testing

23andme celiac disease genetic testing involves assessment of genetic markers associated with gluten sensitivity and celiac disease from your 23andme raw data. The DNA raw data is available to you when you buy the 23andme genetic test for Ancestry.

In recent years, the number of people found to have celiac disease has grown many folds due to increased awareness and ease of diagnosis.

So, why do you need to do genetic testing for coeliac disease? About 1 in 100 people in the U.S have celiac disease. However, 2.5 million people with celiac disease do not know that they have it, i.e they are undiagnosed.

Here are a few important facts about celiac disease genetic testing that everyone must know.

1. 23andme celiac disease testing indicates your risk for celiac disease:  The 23andme celiac disease report interprets 2 genetic haplotypes called HLA-DQ2.5 and HLA-DQ8 HLA-DQ2.5- rs2187668 and HLA-DQ8 -rs7454108. A haplotype refers to a group of genes that are inherited together from one parent. Research studies have shown that people who carry either one or both these two haplotypes constitute 95 percent of all celiac disease incidences.
2. What does celiac disease mean?: Celiac (or coeliac)  disease is an autoimmune condition that occurs in people with a genetic predisposition. In such individuals, gluten, present in wheat, affects the villi in the small intestines.  Gluten is a glue-like protein which is also found in rye, barley and spelt.
3. Is celiac disease hereditary? Celiac disease is hereditary. Individuals with a first degree relative of someone with celiac disease has a one in 10 chance of developing celiac disease.
4. Is celiac disease genetic? Since it is hereditary, it is genetic too. To develop celiac disease, HLA-DQA1 and HLA-DQB1 risk alleles are required but they may not be sufficient for the development of the disease. The HLA-DQ heterodimers, which are encoded by these HLA-DQ alleles, present wheat peptides to CD4+ T cells. This activates the T cells and, thereby, activating an inflammatory immune response in the intestine.
5. What are the symptoms of celiac disease? There are more than 200 symptoms identified for this condition. Among children, celiac disease is associated with diarrhoea, vomiting, short stature, irritability, weight loss or abdominal bloating. Celiac symptoms in adults are more to do with autoimmune condition than about abdominal discomfort. Only one-third of celiac disease adult patients experience diarrhoea, other symptoms include osteoporosis, arthritis, depression, missed menstrual period, canker sores or unexplained anaemia.
6. What is the difference between celiac disease and gluten sensitivity?

1. Genetic testing for celiac disease: HLA DQ testing for gluten sensitivity helps in identifying the presence of genetic variants which have been shown to be associated with an increased risk. However, only 3% of individuals with these genetic variants have been found to develop this condition. Those with high-risk variants should watch out for symptoms or use this test in conjunction with a blood test or an upper endoscopy biopsy. Individuals who do not carry any risk variant will not develop the condition.
   
2. How to interpret 23andme celiac disease results:  23andme celiac disease report focuses on two haplotypes. A considerable percentage of celiac disease incidence is caused due to these two variants.Find your variant in the 23andme raw data- HLA DQ 2.5 (rs2187668)
   

   Genotype HLA DQ 2.5 (rs2187668)	Phenotype
   CC	[Advantage] More likely to be gluten tolerant
   CT	Moderate risk for gluten intolerance
   TT	[Limitation] More likely to be gluten intolerant

   
   Find your variant in the 23andme raw data- HLA DQ 8 (rs7454108)
   

   Genotype	Phenotype
   AA	[Advantage] More likely to be gluten tolerant
   AG	Moderate risk for gluten intolerance
   GG	[Limitation] More likely to be gluten intolerant

1. What is the 23andme celiac disease report missing out?23andme celiac report interprets only HLA DQ2.5 and HLA DQ8, it does not provide the results for HLA DQ 2.2 and HLA DQ 7. The Xcode.Life health report coves more gene variants and SNPs associated with celiac disease and gluten sensitivity than the 23andme celiac report. Besides 23andme raw data, Ancestry DNA raw data, FTDNA raw data and raw data from other companies can also be uploaded.Find your variant in the 23andme raw data- HLA DQ 2.2 (rs2395182, rs7775228,rs4713586)
   

   Genotype	Phenotype
   rs2395182- T	[Limitation] More likely to be gluten intolerant
   rs7775228- G	[Limitation] More likely to be gluten intolerant
   rs4713586-A	[Limitation] More likely to be gluten intolerant

   Find your variant in the 23andme raw data- HLA DQ 8 (rs7454108)
   

   Genotype	Phenotype
   GG	[Advantage] More likely to be gluten tolerant
   AG	Moderate risk for gluten intolerance
   AA	[Limitation] More likely to be gluten intolerant

    
2. What are some of the research studies for celiac disease and HLA DQ gene testing? In a study conducted on  4,918 celiac disease patients and 5,684 controls of European ancestry, the HLA DQ genes under study were found to have a significant association with the risk for celiac disease.
   
   In another study conducted on 754 patients, it was found that DQ2.2, DQ2.5, DQ2.7, and DQ8 could be used to predict >95% of celiac disease patients. This study signifies the importance of testing for all these 6 polymorphisms in order to determine risk. Therefore, 23andme celiac disease report may not be sufficient.To view or order your nutrition report with Xcode, click here.

References:

1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2847618/
2. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2386975/
3. https://www.sciencedirect.com/science/article/pii/S0261561414002180