<<Disclaimer: Verify this information before applying it to your situation.>> Hello Listmates: This is in reference to the question I asked concerning my niece who came back with IgG positive and IgA normal (negative?) per her primary doctor for celiac disease. Right now she is on her cruise eating whatever!! She will see my GI after her return. People answered with both children and adults having celiac from these results. With permission from one of our readers, please let me share the following information: Both IgA and IgG gliadin antibodies are detected in sera of patients with gluten sensitive enteropathy (celiac disease). IgG anti-gliadin antibodies seem more sensitive but are less specific markers for disease compared with IgA class antibodies. IgA anti-gliadin antibodies are less sensitive but are more specific. The IgA antibodies have a specificity of 97% but the sensitivity is only 71%. That means that, if a patient is IgA positive, there is a 97% probability that they have CD. Conversely, if the patient is IgA negative, there is only a 71% probability that the patient is truly negative for CD. Therefore, a positive result is a strong indication that the patient has the disease but a negative result doesn't necessarily mean that they don't have it. False positive results are very uncommon but false negative results can occur. On the other hand, the IgG anti-gliadin antibodies are 91% specific and have an 87% sensitivity. This means that they will show positive results more readily but there isn't as strong a correlation with CD. It is less specific. Patients with other conditions but not afflicted with CD will occasionally show positive results. It can occur in patients with other autoimmune diseases or with no disease association at all. This test might yield false positive results but is less likely to yield false negative results. A sensitive testing protocol includes testing for both IgA and IgG anti-gliadin antibodies since a significant portion of celiac patients (approx. 5%) are IgA deficient. This combined IgA and IgG anti-gliadin antibody assay has an overall sensitivity of 95% with a specificity of 90%. The primary reason to test for the IgG gliadin antibody is to catch these patients who are IgA deficient. It is known that the IgA deficient patients usually have higher levels of IgG antibodies to gliadin. As to your question about a diagnosis based upon the IgG gliadin results alone, - - No!! The diagnosis cannot be made based only on these results. IgG anti-gliadin antibodies are detectable in approximately 21% of patients with other gastrointestinal disorders. Immunology is fairly accurate but it is far from being an exact science. All of the lab tests, regardless of the type or source, are presented as "aids to diagnosis". They cannot be used alone as a basis for diagnosis but rather are intended to be considered in conjunction with the physical examination of the patient as well as the reported symptoms, etc. by a trained physician. My note: Since my sister has rheumatoid arthritis and was diagnosed with colon cancer over 8 years ago (still in remission or considered cured), Tom suggested she definitely see a GI if not for celiac but for some other problem. Thanks Tom --- for your wealth of information. Cindy in NJ