Insulin, IgG antibodies
Why this test?
For differential diagnosis of type 1 and type 2 diabetes.
To make a prognosis for the development of type 1 diabetes in patients with a heavy hereditary history of this disease, especially children.
In what cases is it prescribed?
When examining a patient with clinical signs of hyperglycemia: thirst, increased daily urine volume, increased appetite, weight loss, progressive vision loss, decreased sensitivity of the skin of the extremities, formation of foot and leg ulcers that do not heal for a long time
When examining a patient with a heavy hereditary history of type 1 diabetes, especially if it is a child.
Insulin antibodies (AT to insulin) are autoantibodies produced by the body against its own insulin. They are the most specific marker of type 1 diabetes (type 1 diabetes) and are studied for the differential diagnosis of this disease. Type 1 diabetes (insulin-dependent diabetes) occurs as a result of autoimmune damage to the cells of the pancreas, which leads to a complete lack of insulin in the body. This distinguishes type 1 DM from type 2 DM, in which immunological disorders play a much smaller role.
Differential diagnosis of types of DM is of fundamental importance for making a prognosis and treatment tactics. Autoantibodies directed against the cells of the islets of Langerhans are studied for the differential diagnosis of variants of DM. The vast majority of patients with type 1 diabetes have antibodies to components of their own pancreas. Conversely, such autoantibodies are not characteristic of patients with type 2 diabetes. Insulin is an autoantigen in the development of type 1 diabetes. Unlike other known autoantigens found in this disease (glutamate decarboxylase and various proteins of the islets of Langerhans), insulin is the only autoantigen strictly specific for the pancreas.
Therefore, a positive blood pressure test for insulin is considered the most specific marker of autoimmune damage to the pancreas in type 1 diabetes (insulin autoantibodies are found in the blood of 50% of patients with type 1 diabetes). Other autoantibodies that are also found in the blood of patients with type 1 diabetes include antibodies to islet cells of the pancreas, antibodies to glutamate decarboxylase, and some others. At the time of diagnosis, 70% of patients have 3 or more types of antibodies, less than 10% have only one type, and 2-4% have no specific autoantibodies. At the same time, autoantibodies in type 1 diabetes are not the direct cause of the development of the disease, but only reflect the destruction of pancreatic cells.
Blood pressure before insulin is most characteristic of children with type 1 diabetes and is much less common in adult patients.
As a rule, in children's patients, they occur first in a very high titer (this tendency is especially pronounced in children under 3 years of age). In view of these features, blood pressure analysis before insulin is considered the best laboratory test to confirm the diagnosis of type 1 diabetes in children with hyperglycemia. However, it should be noted that a negative result does not exclude the presence of type 1 diabetes. In order to obtain the most complete information during diagnosis, it is recommended to analyze not only BP to insulin, but also other autoantibodies specific for type 1 diabetes.
Detection of blood pressure before insulin in a child without hyperglycemia is not considered in favor of the diagnosis of type 1 diabetes. With the course of the disease, the level of blood pressure to insulin decreases to undetermined values, which distinguishes these antibodies from other type 1 diabetes-specific antibodies, the concentration of which remains stable or increases? Despite the fact that blood pressure to insulin is considered a specific marker of type 1 diabetes, cases of type 2 diabetes have been described, in which it was also possible to detect these autoantibodies. Type 1 diabetes has a pronounced genetic orientation. Most patients with this disease are carriers of certain HLA-DR3 and HLA-DR4 alleles.
The risk of developing type 1 diabetes in close relatives of a patient with this disease increases 15 times and is 1:20. As a rule, immunological disorders in the form of the production of autoantibodies to the components of the pancreas are registered long before the onset of type 1 diabetes. This is due to the fact that the development of extensive clinical symptoms of type 1 DM requires the destruction of 80-90% of the cells of the islets of Langerhans. Therefore, the blood pressure test before insulin can be used to assess the risk of developing diabetes in the future in patients with a heavy hereditary history of this disease. The presence of blood pressure to insulin in the blood of such patients is associated with a 20 percent increase in the risk of developing type 1 diabetes in the next 10 years. Detection of 2 or more autoantibodies specific for type 1 diabetes increases the risk of developing the disease by 90% in the next 10 years.
Despite the fact that the analysis of blood pressure before insulin (as well as any other laboratory parameters) is not recommended as a screening for type 1 diabetes, the study may be useful in the examination of children with a burdened hereditary history of type 1 diabetes . Together with the glucose tolerance test, it allows diagnosing type 1 diabetes before the development of pronounced clinical symptoms, including diabetic ketoacidosis.
The level of C-peptide at the time of diagnosis will also be higher, reflecting the better indicators of residual cell function observed with this strategy of managing at-risk patients. Most patients who receive insulin preparations (exogenous, recombinant insulin) eventually develop antibodies to it. They will have a positive test result regardless of whether they produce antibodies to endogenous insulin or not.
Because of this, the study is not intended for the differential diagnosis of type 1 DM in patients who already received insulin preparations. Such a situation may arise when type 1 diabetes is suspected in a patient misdiagnosed with type 2 diabetes who was treated with exogenous insulin to correct hyperglycemia. Most patients with type 1 diabetes have one or more concomitant autoimmune diseases.
Autoimmune diseases of the thyroid gland (Hashimoto's thyroiditis or Graves' disease), primary adrenal insufficiency (Addison's disease), gluten enteropathy (celiac disease) and pernicious anemia are most often diagnosed. Therefore, with a positive result of blood pressure analysis before insulin and confirmation of the diagnosis of type 1 diabetes, it is necessary to conduct additional laboratory tests to rule out these diseases.