Gliadin, IgA antibodies
Why this test?
For diagnosis of celiac disease and its treatment control.
For an objective assessment of the introduction of a gluten-free diet.
In what cases is it prescribed?
With symptoms of celiac disease: periodic vomiting, diarrhea, growth retardation (children), abdominal pain, anemia, epilepsy, atopic dermatitis, angular cheilitis, aphthae, Dühring's herpetiform dermatitis, signs of vitamin deficiency - visual impairment, neuropathy, osteopenia, increased bleeding , amenorrhea, infertility, impotence (adults);
When examining a patient with a heavy family history of celiac disease;
Control of celiac disease treatment;
Wwhen examining a patient with type 1 diabetes, Hashimoto's autoimmune thyroiditis, total alopecia, systemic connective tissue diseases, and Down syndrome.
IgA gliadin antibodies are class A immunoglobulins produced in the body of susceptible individuals in response to ingestion of gluten-containing products.
Gluten can be found in large quantities in the grains of wheat, rye, barley, oats and some other cereals. One of the components of gluten, gliadin, is able to trigger an immune response, which is accompanied by the production of specific anti-gliadin antibodies.
Antibodies to gliadin are deposited in the mucous membrane of the small intestine, which initiates an inflammatory reaction and leads to atrophy of the mucous membrane. The result of this immunological response is gluten enteropathy (celiac disease).
Normally, food components do not lead to the formation of an immune response, therefore, the detection of antibodies to gliadin is a pathological sign that should alert the doctor even if the patient does not have any complaints or specific symptoms.
Quite often, celiac disease is not accompanied by pronounced clinical symptoms, but is manifested by impaired absorption of vitamins and trace elements. In view of these features, research on antibodies to gliadin should be prescribed not only in case of obvious signs of this disease, but also in the examination of patients with non-specific complaints of weakness and weight loss. In addition, manifestations of celiac disease can be Düring's herpetiform dermatitis, atopic dermatitis, alopecia, aphthae, etc.
The high sensitivity (82-87%) of the test for IgA-antibodies to gliadin is considered a good screening test for the diagnosis of celiac disease. However, it should be noted that the specificity of the test is 83-85%, which does not exclude the possibility of false positive results.
Detection of IgA-antibodies to gliadin is also possible in some other diseases (systemic lupus erythematosus, liver diseases, rheumatoid arthritis) even in the absence of celiac disease. In addition, anti-gliadin antibodies are found in 4% of healthy people. Therefore, with a positive result of this screening test, a confirmatory test should be conducted, which is characterized by higher specificity - a test for antibodies to endomysium (specificity - 100%). The probability of celiac disease with positive results of screening and confirmatory tests is 99.1%.
The diagnosis must be confirmed by histological examination of a sample of the mucous membrane of the small intestine. Diagnosis of celiac disease in patients with selective deficiency of immunoglobulin A presents a certain difficulty. The prevalence of this form of congenital immunodeficiency among patients with celiac disease is higher than among healthy people, and is 2-3%.
Since patients with selective IgA deficiency do not produce this immunoglobulin at all, the test for IgA-antibodies to gliadin in them will be characterized by a pseudo-negative result. In view of this feature, it is recommended to supplement research on IgA antibodies with research on IgG antibodies to gliadin and antibodies to tissue transglutaminase. In addition, it is necessary to rule out immunoglobulin A deficiency.
Celiac disease is characterized by a pronounced genetic predisposition, it is associated with certain alleles: HLA-DQ-2 and HLA-DQ-8. Its prevalence among relatives of celiac patients is much higher than the average in the population. Thus, the probability of detecting signs of celiac disease in a relative of the first line of kinship is about 10%. Therefore, with a positive result of the study and confirmation of the diagnosis, it is advisable to conduct a laboratory examination of the patient's family members.
The immune response to dietary gliadin fades after a gluten-free diet. Therefore, the analysis of IgA-antibodies to gliadin can be used to control the treatment of the disease, as well as to objectively assess adherence to a gluten-free diet. As a rule, against the background of a strict gluten-free diet, the level of IgA-antibodies to gliadin becomes negative. For the same reason, it is better to donate blood for research before prescribing a gluten-free diet. Celiac disease is often combined with other autoimmune diseases, such as type 1 diabetes, Hashimoto's autoimmune thyroiditis, and systemic connective tissue diseases. Therefore, the examination of a patient with celiac disease includes additional laboratory tests that exclude concomitant diseases.