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Celiac.com 02/05/2023 - If you have celiac disease symptoms, for example chronic diarrhea, anemia, bloating, abdominal pain, rashes, are in a higher risk group, etc., your doctor may order a blood test for celiac disease. Note that before doing any blood tests for celiac disease you must be eating gluten for a while beforehand, and the amount and length of time can vary, but is somewhere between 2 slices of wheat bread daily for 6-8 weeks and 1/2 slice of wheat bread or 1 wheat cracker for 12 weeks, otherwise you may end up with false negative results. For a celiac disease antibody test, a clinician collects a small amount of the patient's blood. The sample is then sent to a lab, where the blood cells are then removed, and the test is conducted. Celiac Disease Blood Tests Note that the accuracy and specificity of each test can vary depending on the laboratory performing the test, the specific method used, and the population being tested. Sensitivity refers to the ability of a test to correctly identify individuals with the condition (true positive rate), while specificity refers to the ability of a test to correctly identify individuals without the condition (true negative rate). tTG-IgA (tissue transglutaminase IgA) Blood Test for Celiac Disease This test measures the levels of IgA antibodies to tissue transglutaminase, an enzyme that is involved in the immune response to gluten in those who have celiac disease. The test is estimated to have a sensitivity of approximately 90%, which means that it correctly identifies 90% of people with celiac disease. It also has a high specificity of around 95%, which means that it correctly identifies 95% of people who do not have celiac disease. Other Names for the tTG-IgA Test: Tissue Transglutaminase IgA Test Anti-Tissue Transglutaminase IgA Test tTG-IgA Blood Test tTG-IgA Serology Test IgA-tTG Antibody Test Tissue Transglutaminase Antibody IgA Assay tTG-IgG (tissue transglutaminase IgG) Blood Test for Celiac Disease This test measures the levels of antibodies to tissue transglutaminase, but it specifically measures IgG antibodies rather than IgA antibodies which are produced in people who eat gluten and have celiac disease. It is not as sensitive or specific as the tTG-IgA test, but it may be useful in cases where a person has an IgA deficiency, which can occur in approximately 2-3% of people with celiac disease. In these cases, the tTG-IgG test may be positive while the tTG-IgA test is negative. However, the tTG-IgG test is not recommended as a first-line screening test for celiac disease. The sensitivity of the tTG-IgG blood test is generally high, ranging from 85% to 98%. This means that the test can accurately detect celiac disease in a significant percentage of people who have the condition. The specificity of the tTG-IgG blood test is also high, typically around 90% to 98%. This indicates that the test can effectively rule out celiac disease in individuals who do not have the condition. Other Names for the tTG-IgG Test: Tissue Transglutaminase IgG Test Anti-Tissue Transglutaminase IgG Test tTG-IgG Blood Test tTG-IgG Serology Test IgG-tTG Antibody Test Tissue Transglutaminase Antibody IgG Assay EMA-IgA (endomysial antibodies IgA) Blood Test for Celiac Disease This is a highly accurate test for celiac disease, that requires specialized expertise to perform and interpret, and it is more expensive than other blood tests. It is generally used as a last test to confirm celiac disease after a positive tTG-IgA test. The sensitivity of a test refers to its ability to correctly identify individuals with the condition. For the EMA-IgA blood test, the sensitivity is generally very high, ranging from 90% to 98%. This means that the test can accurately detect celiac disease in a significant percentage of people who have the condition. The specificity of a test refers to its ability to correctly identify individuals without the condition. For the EMA-IgA blood test, the specificity is also high, typically around 95% to 100%. This indicates that the test can effectively rule out celiac disease in individuals who do not have the condition. Other Names for the EMA-IgA Test: Endomysial Antibodies IgA Test Anti-Endomysium Antibodies IgA Test Endomysial Antibody IgA Assay EMA IgA Blood Test EMA-IgA Serology Test Endomysium IgA Ab DGP-IgA and DGP-IgG (Deamidated Gliadin Peptide) Blood Tests for Celiac Disease These tests measure the levels of antibodies in the blood, but specifically targets deamidated gliadin peptides, which are a type of gluten protein that can trigger an immune response in people with celiac disease. The tests are not always included in adults, but should be in cases with IgA deficiency. The tests should always be included when screening children, especially if they are under 2 years old. The DGP tests were created to detect celiac disease in those with IgA deficiency, and there are here is more information about them: DGP-IgA Test: This test measures the levels of IgA antibodies specific to deamidated gliadin peptide. IgA antibodies are produced by the immune system in response to gluten exposure. In individuals with celiac disease who produce normal levels of IgA, a positive DGP-IgA test result suggests the presence of ongoing immune response to gluten. DGP-IgG Test: The DGP-IgG test measures IgG antibodies against deamidated gliadin peptide. IgG antibodies are another type of immune response and may be elevated in individuals with celiac disease who have IgA deficiency (a common occurrence in celiac disease). The DGP-IgA test is considered to have high sensitivity and specificity. In general, the DGP-IgA test has been reported to have a sensitivity ranging from 75% to 95% and a specificity ranging from 90% to 100%. Overall, the DGP tests, including DGP-IgA and DGP-IgG, exhibit a sensitivity of approximately 85-95% and a specificity of about 95-98%. Other Names for the DGP-IgA Test: Gliadin Peptide Antibody IgG (Immunoglobulin A) Anti-Gliadin Antibody IgA (AGA IgA) Anti-Gliadin IgA Antibody (AGA IgA) Anti-Gliadin IgA (AGA IgA) Anti-Gliadin Immunoglobulin A Antibody (AGA IgA) Anti-Deamidated Gliadin Peptide IgA (DGP IgA) Anti-Deamidated Gliadin Antibody IgA (DGP IgA) The sensitivity of the DGP-IgG test is reported to range from 75% to 85%, which means it can correctly identify individuals with the condition in about 75% to 85% of cases. The specificity of the DGP-IgG test is reported to range from 75% to 95%, which means it can correctly identify individuals without the condition in about 75% to 95% of cases. Overall, the DGP tests, including DGP-IgA and DGP-IgG, exhibit a sensitivity of approximately 85-95% and a specificity of about 95-98%. Other Names for the DGP-IgG Test: Gliadin Peptide Antibody IgG (Immunoglobulin G) Anti-Gliadin Antibody IgG (AGA IgG) Anti-Gliadin IgG Antibody (AGA IgG) Anti-Gliadin IgG (AGA IgG) Anti-Gliadin Immunoglobulin G Antibody (AGA IgG) Anti-Deamidated Gliadin Peptide IgG (DGP IgG) Anti-Deamidated Gliadin Antibody IgG (DGP IgG) IgA Levels/Deficiency Blood Test This should always be included in any blood panel for celiac disease, but it does not test directly for celiac disease, and is done to determine the accuracy of the other blood tests. People who are IgA deficient may score lower, of have no measurable levels on certain celiac disease blood tests. This test measures the levels of Immunoglobulin A (IgA) in the bloodstream. IgA is an important antibody that plays a significant role in the immune system, particularly in protecting the body's mucosal surfaces (e.g., respiratory and digestive tracts). Low IgA levels can indicate IgA deficiency, a condition where the body does not produce enough IgA, leading to an increased risk of infections and other health issues. The IgA Levels/Deficiency Test helps healthcare providers diagnose and monitor IgA-related conditions. Other Names for the IgA Levels/Deficiency Test: Immunoglobulin A (IgA) Test Total IgA Test Serum IgA Test IgA Serum Levels Test IgA Blood Test IgA Quantitative Test IgA Antibody Test IgA Immunodeficiency Test Celiac Disease Blood Antibody Screening is ~98% Accurate in Adults Using the Mayo Clinic Protocol A celiac disease blood panel includes several tests to determine whether someone has celiac disease. These tests are very specific because certain antibodies only appear in those with gluten sensitivity, celiac disease and/or dermatitis herpetiformis. Testing begins with a test called Immunoglobulin A (IgA). If the results are normal, then a Tissue transglutaminase, antibody, IgA test is given. A weak positive should lead to the following tests: Endomysial antibodies (IgA) and; Gliadin (deamidated) antibody, IgA. If the initial Immunoglobulin A (IgA) test is lower than normal, then these two tests should be done: Tissue transglutaminase antibodies, IgA and IgG profle. Gliadin (deamidated) antibodies evaluation, IgG and IgA. If the initial Immunoglobulin A (IgA) test is below the level of detection (<1.0 mg/dL), then these two tests should be done: Tissue transglutaminase (tTG) antibody, IgG. Gliadin (deamidated) antibody, IgG. It sounds complicated, but it's pretty standard procedure now, and when blood screening is done this way the results for celiac disease are ~98% accurate. Many People Can Be Diagnosed Using Only Blood Tests and No Biopsy According to the latest research, if the blood test results are at certain high levels that range between 5-10 times the reference range for a positive celiac disease diagnosis, it may not be necessary to confirm the results using an endoscopy/biopsy: Blood Test Alone Can Diagnose Celiac Disease in Most Children and Adults TGA-IgA at or Above Five Times Normal Limit in Kids Indicates Celiac Disease in Nearly All Cases No More Biopsies to Diagnose Celiac Disease in Children! Biopsy Still Standard in Adult Celiac Diagnosis After positive blood tests some doctors still require a biopsy to confirm the diagnosis. However, this is changing, as new techniques allow doctors to accurately detect celiac disease in adults without a biopsy. Remember, nearly all tests and screening for celiac disease require the patient to be eating a gluten-containing diet before testing, usually you should be eating at least 1/2 slice of wheat bread or 1 wheat cracker daily for at least 2 weeks before the endoscopy. Be sure to check with your doctor for the latest protocol. Blood Tests for Follow Up Care Blood tests may also be useful in follow up care in those with celiac disease to confirm that their diet is indeed free of gluten. Also, because of the lack of standardization, keep in mind that blood test results may not be directly comparable from one lab to the next. More Celiac Disease Testing Resources What is a Gluten Challenge and How Long Must it Last? Interpretation of Celiac Disease Blood Test Results Ten Facts About Celiac Disease Genetic Testing Blood Test Questions on the Celiac Disease and Gluten-Free Forum Test results and question about gluten challenge How Long To Eat Gluten For Accurate Blood Test Read more at mayocliniclabs.com

Celiac.com 10/24/2012 - Doctors can face challenges when attempting to diagnose celiac disease in patients who have already begun a gluten-free diet, and/or when the results of tests are inconsistent. To better understand this problem, a group of researchers set out to assess the benefits of an in vitro gliadin challenge. The research team included Raffaella Tortora, MD, Ilaria Russo, PhD, Giovanni D. De Palma, MD, Alessandro Luciani, PhD, Antonio Rispo, MD, Fabiana Zingone, MD, Paola Iovino, MD, Pietro Capone, MD and Carolina Ciacci, MD. The study cohort included 57 patients without celiac disease, 166 patients with untreated celiac disease, 55 patients with celiac disease on a gluten-free diet, and 59 patients with challenging diagnosis. The team provided all patients with endoscopy for collection of duodenal samples, which served for the diagnosis of celiac disease and for the in vitro evaluation of the gliadin-induced mucosal expression of seven inflammatory markers: PY99, ICAM-1 (intercellular cell adhesion molecule), HLA-DR, CD3, CD25, CD69, and transglutaminase 2 IgA. Diagnostic work-up for celiac disease included the search of specific serum antibodies. Researchers asked patients in the challenging diagnosis group to stop gluten-free diet to facilitate the search for these antibodies under untreated conditions. They used the area under the receptor-operated curve (ROC) for statistical analyses on accuracy. For patients with and without celiac disease (not including those on a gluten-free diet) HLA-DR offered the best accuracy for diagnosing celiac disease (area under ROC = 0.99). Combining the data from the HLA-DR with data of other markers did not increase test accuracy. The team found similar results in the 39 patients of the difficult diagnosis group undergoing the search celiac disease-speciï¬c antibodies under untreated conditions. In vitro testing of mucosal HLA-DR to gliadin is an accurate tool for the diagnosing celiac disease, and also works in patients who are hard to diagnose. Source: Am J Gastroenterol 2012; 107:111–117; doi:10.1038/ajg.2011.311; published online 27 September 2011

Question: Do I have to re-introduce gluten in order to have an accurate gluten sensitivity test done? Answer: Yes and No If a person knows they are sensitive to gluten and have gone on a gluten-free diet, and want to know if they can have gluten again, then a challenge is in order (reintroduce gluten). THIS IS STRONGLY NOT RECOMMENDED. The gluten challenge has many cases of people who were damaged (some permanently) from the reaction to reintroducing gluten Even Small Amounts of Gluten Cause Relapse in Children With Celiac Disease, Journal of Pediatric Gastroenterology and Nutrition 34:26­30, and it is no longer a requirement for diagnosing celiac disease Am J Clin Nut 1999;69:354-65. Among 374 children in whom celiac disease was diagnosed before the age of 2, 5% developed an auto-immune disorder while on a gluten-free diet. Of those who went gluten-free, had years of no symptoms, then went back on a gluten-containing diet, 3.65% prevalence of systemic auto-immune disease with less than 12 months of eating gluten 9.1 % prevalence for 13-36 months of eating gluten again 26.3% prevalence for > 36 months of eating gluten again This means 1 out of 4 people who were sensitive to gluten, went gluten-free and eliminated all of their symptoms developed auto-immune diseases within 3 years of eating gluten again. Gastroenterology 1999;117:297-303. If you know you are Gluten Sensitive, and you've gone on a gluten-free diet, and you want to know "am I better", then testing will confirm you are being successful in 'quieting down' the inflammatory cascade that occurs with gluten sensitivity and which sets one up for the development of autoimmune disease. And if you want to 'throw the dice', if you want to gamble that you won't be the '1 out of 4' who develops an autoimmune disorder, then you would want to first check and make sure your tests are negative while being on a gluten-free diet, then do your gluten challenge and test again 1-2 months later. Once again, not recommended to do this. Many people do not develop celiac disease until later in life. So even if one tests negative now, if they're genetically vulnerable, celiac disease can develop at any time as a result of the body no longer able to handle the stress of life. Something will be the 'straw that broke the camels back' and a person who has had negative tests in the past will begin producing the antibodies and begin the tissue destruction that will eventually manifest as Gluten Sensitivity and/or celiac disease. So in this scenario, these people want to know if they're genetically vulnerable. The question is, am I sensitive to wheat? When a test looking at Gluten Sensitivity comes back positive, it tells us the immune system is reacting to an exposure to gluten. And if you are not eating gluten, it's one of a few things: A hidden exposure to gluten A cross-reactive food A cross-reactive virus or bacteria A poorly functioning GI Tract (consider Array #2-Intestinal Antigenic Permeability Screen) An unknown cause (potentially Refractory Sprue).

Celiac.com 08/04/2011 - People who use direct-to-consumer genetic tests sold by deCODEme and 23andMe frequently receive misleading results, because these tests do not accurately predict risk factors. So say two geneticists, who conducted two studies that assessed the accuracy of test predictions relative to various known disease risks. Presenting their results from both studies at the annual conference of the European Society of Human Genetics, the scientists have gone so far as to call for a ban on the tests. The first study was conducted by Rachel Kalf, from the department of epidemiology at Erasmus University Medical Centre in Rotterdam. Using established genotype frequencies, Kalf simulated genotype data for 100,000 individuals. She then used the formulas and risk data provided by the test companies to predict risks for eight common multi-factorial diseases: age-related macular degeneration (AMD); atrial fibrillation; celiac disease; Crohn's disease; heart attack; prostate cancer; and Type 1 and Type 2 diabetes (T2D). Kalf noted that both companies assigned an increased risk to a substantial part of the test group. However, Kalf says the risk of disease in this group was often substantially lower than the risk in the rest of the study group. For example, for AMD, which has the highest predictive ability of all eight diseases, both companies assumed that the risk in the population was around 8 percent. However, among subject assigned an increased risk factor, 23andMe estimated risk at 16 percent, while deCODEme's estimated that 19 percent would develop AMD. This contrasts with a risk of about 4 percent for the rest of the study population. This means that people in the higher risk group may have a four-fold increased risk of disease, but "are still far more likely not to develop the disease at all," explains co-researcher Cecile Janssens. For T2D, using the risk levels of about 25 percent assigned by the companies, 32 percent of those in the higher risk group would actually develop T2D compared to just 22 percent in the rest of the study population. "This difference in disease risk is too small to be of relevance," says Janssens. Source: Science Blog