Gliadin, IgG antibodies
Why this test?
For diagnosis of celiac disease and control of its treatment.
For an objective assessment of the introduction of a gluten-free diet for a patient.
In what cases is it prescribed?
With symptoms of celiac disease: periodic vomiting, diarrhea, growth retardation (in 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 (in adults);
when examining a patient with a heavy family history of celiac disease;
in the control of treatment of celiac disease;
when examining a patient with type 1 diabetes, Hashimoto's autoimmune thyroiditis, total alopecia, systemic connective tissue diseases, and Down syndrome.
Antibodies to gliadin IgG are immunoglobulins of class G, produced in the body of susceptible individuals in response to the ingestion of gluten in the intestine. Gluten is found in large quantities in some cereals (barley, wheat, rye, oats) and is present in many food products (bread, beer, pasta, cookies). It is, in fact, gluten and consists of several proteins: prolamin and glutelin. The main prolamin of wheat is gliadin. In susceptible individuals, the use of gluten-containing products is accompanied by the production of antibodies to gliadin, which are deposited in the mucous membrane of the small intestine.
Gluten-induced immune-mediated damage to the mucous membrane of the small intestine eventually leads to its atrophy (gluten enteropathy), which is accompanied by symptoms of malabsorption in the form of diarrhea, weight loss, deficiency of trace elements and vitamins, and anemia.
The peculiarity of gluten enteropathy (celiac disease) is that with timely diagnosis and adherence to a strict gluten-free diet, its symptoms disappear. One of the methods of screening for the disease is the detection of antibodies to gliadin in the blood of patients.
Antibodies to gliadin refer to immunoglobulins of class A and G. The study of IgG antibodies to gliadin is generally characterized by lower sensitivity and specificity than the study of IgA antibodies. However, as a rule, laboratory diagnosis of gluten enteropathy includes analysis of both classes of immunoglobulins. The combination of the two studies increases the probability of detecting antibodies in the serum of a patient who actually suffers from gluten enteropathy. In addition, the test for IgG antibodies is especially useful in the combination of gluten enteropathy and hereditary deficiency of immunoglobulin A, which is observed in 2-3% of cases of celiac disease.
Determination of only IgA antibodies in such patients will lead to a false negative result. For the same reason, the analysis of IgG antibodies to gliadin is recommended to be supplemented with the measurement of total immunoglobulin A concentration. It is important to note that the diagnosis of gluten enteropathy is a comprehensive assessment of immunological abnormalities, clinical signs, the effect of a gluten-free diet and histological examination data.
A positive result of this analysis is not interpreted in favor of celiac disease in the absence of symptoms and other markers of the disease. On the other hand, a negative result does not exclude the presence of celiac disease. When following a strict gluten-free diet, the titer of IgG antibodies to gliadin is significantly reduced, which allows the use of this laboratory marker to monitor the treatment of the disease and objectively assess the patient's adherence to the prescribed diet. For the same reason, it is better to donate blood for research before prescribing a gluten-free diet. Gluten enteropathy is a multifactorial disease with a pronounced genetic component.
Thus, among close relatives of the patient, it occurs in 10% (against 1% in the population). In this regard, the patient's relatives are also subject to examination, which includes a test for IgG antibodies to gliadin. In addition, the prevalence of gluten enteropathy is higher among patients with type 1 diabetes, Hashimoto's autoimmune thyroiditis, Down syndrome, and systemic connective tissue diseases, so the examination of such patients should also include an analysis of IgG antibodies to gliadin.
The main purpose of the analysis is to identify patients subject to further investigation for endoscopy and biopsy of the small intestine.
Since endoscopy is an invasive study associated with certain risks, some clinicians have recently suggested replacing this stage of diagnosis with a comprehensive and complete laboratory screening of gluten enteropathy.
In addition to IgG-antibodies to gliadin, it also includes IgA-antibodies to gliadin, antibodies to tissue transglutaminase (IgA and IgG) and antibodies to endomysium. Anti-gliadin antibodies are not strictly specific for gluten enteropathy. IgG antibodies are found in irritable bowel syndrome, dyspepsia, primary biliary cirrhosis, autoimmune hepatitis, nonspecific ulcerative colitis and Crohn's disease, sarcoidosis, as well as Dühring's herpetiform dermatitis, eczema, and bullous pemphigoid.