Anti-Insulin Antibodies

Some diabetic patients form antibodies to the insulin they take. These antibodies bind with some of the insulin, making less insulin available for glucose metabolism and necessitating increased insulin dosages. This phenomenon is known as insulin resistance.

Performed on the blood of a diabetic patient receiving insulin, the anti­insulin antibody test detects insulin antibodies. Insulin antibodies are immunoglobulins, called anti-insulin Ab. The most common type of anti-insulin Ab is immunoglobulin G (IgG), but anti-insulin Ab is also found in the other four classes of immunoglobulins­IgA, IgD, IgE, and IgM. IgM may cause insulin resistance, and IgE has been associated with allergic reactions.

Purpose

• To determine insulin allergy.
• To confirm insulin resistance.
• To determine if hypoglycemia is caused by insulin overuse.

Patient Preparation

• Tell the patient that this test is used to determine the most appropriate treatment for his diabetes and to determine if he has insulin resistance or an allergy to insulin.
• Tell the patient that the test requires a blood sample and who will perform the venipuncture and when.
• Tell the patient that although he may experience transient discomfort from the needle puncture and the tourniquet, collecting the sample takes only a few minutes.
• Tell him that he needn't fast before the test.
• Ask the patient if he has had a radio­active test recently; if so, note this on the laboratory slip.

Procedure And Posttest Care

• Perform a venipuncture, and collect the sample in a 7-ml red-top tube.
• If a hematoma develops at the venipuncture site, apply warm soaks.

Precautions

• Handle the sample gently to prevent hemolysis.

Normal Findings

There should be less than 3% binding of the patient's serum with labeled beef, human, and pork insulin.

Abnormal Findings

Elevated levels may occur in insulin allergy or resistance and in factitious hypoglycemia.

Interfering Factors

• Radioactive test performed within 1 week before the test