IMMUNOGLOBULIN IgG

Also Known As: Immunoglobin test, IgG test

What Is Immunoglobin Test?

It is a laboratory test for the evaluation of the immune system of your body. It measures the number of antibodies formed in your body. Antibodies (immunoglobins) are the protein structures produced by a special type of white blood cell called B-cell or Plasma cells. Your immune system produces antibodies to fight against invading bacteria, viruses, fungus, cancer cells, and foreign bodies. Antibodies attach to antigens present on the pathogen's surface so that the defense system recognizes them and kills them. Sometimes, the immune system produces antibodies against the body's own cells, thus destroying them without any cause; such diseases are called autoimmune diseases.

The five types of antibodies are;

IMMUNOGLOBIN A: It is found in mucous membranes of the respiratory tract, gastrointestinal tract, sinuses, saliva tears, and breast milk. The normal range is 0.8-3g/L. IgA has two subtypes, IgA1 and IgA2.

IMMUNOGLOBIN M: Largest antibody, and it is the first line of defense after infection and is mainly found in blood and lymphatic fluids. The normal range is 0.4-2.5g/L.

IMMUNOGLOBIN G: It is the most common antibody (75%) of all the antibodies in your body and is mainly found in blood and almost all body fluids. It is the smallest and the only antibody that can cross the placenta and reach the fetus. It forms late after an infection or immunization and protects your body against infection by remembering which foreign organism you have been exposed to before. The normal range lies between 6-16g/L, and there are four subtypes of IgG that is IgG1, IgG2, IgG3, and IgG4. 

IMMUNOGLOBIN E: These are present in small amounts, and a higher level occurs due to the body's overwhelming response to allergens and parasites. They are involved in allergic reactions against medicines, poisons, pollen, dust, animal dander, feathers, and fungal spores.

IMMUNOGLOBIN D: It is the least understood antibody and is found in a very small quantity in the body. It is not routinely tested.

The amount of each type of immunoglobin in your blood helps your healthcare provider detect the cause of illness. Too low levels make you susceptible to infections, and too high levels may suggest an allergic reaction or over-active immune system.

What Is The Test Used For?

The test is used to determine the total amount of specific types of immunoglobins (usually primary immunoglobins IgG, IgA, IgM) in your body and to monitor the conditions that can affect the immune status of your body, either genetic or acquired. Immune disorders can be classified as:

IMMUNOGLOBIN EXCESS (HYPERGAMAGLOBINEMIA): Increased immunoglobins can be polyclonal, meaning all classes of immunoglobins are produced from many plasma cells, or monoclonal which means all excess immunoglobins are formed from a single clone of plasma cells.

IMMUNOGLOBIN DEFICIENCY (HYPOGAMAGLOBINEMIA): decreased amount of immunoglobin can be caused by Primary (inherited) disorders in which the body cannot produce an adequate amount of antibodies. Secondary (acquired) deficiency is the most common type, mainly caused by underlying factors or conditions.

Why And When Do You Need To Get Tested?

This test helps investigate and monitor various immune disorders and conditions that can affect the level of immunoglobins in your body. Your healthcare practitioner may suspect an immune disorder and request this test if you experience the signs and symptoms of immunoglobin deficiency or excess, which may include:

• Persistent diarrhea
• Unexplained weight loss
• Fever without any explained cause
• Skin rashes
• Frequent allergic reactions and history of allergies
• Traveling sickness
• Known conditions like multiple myeloma (a type of blood cancer) and HIV/AIDs.
• Failure to thrive
• Recurrent sinus and lung infections
• Known autoimmune disorders like lupus, celiac disease, and rheumatoid arthritis.

The test is also used to check the protection from an immunization status infection. Moreover, it is used for evaluation and monitors the response of ongoing treatment, thus helping in accessing the need for treatment modification.

What Kind Of Sample Is Required?

A blood sample is taken from the vein in your arm or hand by using a small needle which is then transferred into a test tube or vial. A finger stick test is sometimes performed on children where a blood sample is taken on the glass slide. Cerebrospinal fluid is obtained via lumbar puncture (also called a spinal tap), in which a hollow needle is inserted between two vertebrae of your lower spine by your healthcare provider, and a small amount of fluid is collected in a test tube or vial. For the collection of saliva or other fluids of the body, a container is provided by the laboratory.

Do You Need To Prepare For This Test?

You need no special preparation for this test.

Are There Any Risks To This Test?

It is a safe test with minimal risks; when a blood sample is taken, you may feel temporary drowsiness, pain, sting, or mild bruising at the site of the needle prick. Very rarely, you may develop infection or bleeding at the prick site. While taking CSF, you may experience discomfort or mild to moderate pain in your back which usually goes away quickly.

What Does Test Result Mean?

The test results are usually obtained within a few days. Abnormal results suggest that something is affecting your immune system. An Immunoglobin test is not a diagnostic test but provides a strong indication of the disease or condition. Multiple conditions cause your body to produce too many or too few immunoglobins.

A high level of immunoglobin means your body is excessively producing antibodies. Causes may include:

Polyclonal antibodies (IgG IgM IgA) increase in:

• Acute and chronic infections
• Autoimmune diseases (lupus, juvenile rheumatoid arthritis, celiac disease, scleroderma)
• Chronic inflammatory diseases (Irritable bowel disease)
• Wiskot-Aldrich syndrome
• Infections contracted to newborns during pregnancy like syphilis, toxoplasmosis, and rubella.

Monoclonal antibodies increase in:

• Multiple myeloma
• Lymphoma
• Waldenstrom's macroglobulinemia
• MGUS (monoclonal gammopathy of undetermined significance)

Low levels of immunoglobins suggest that your immune system is not working properly causes include:

• Drugs like carbamazepine, phenytoin, immunosuppressant, and steroids.
• Kidney and liver disease.
• Complicated diabetes.
• Burns
• Protein-losing enteropathy
• Agammaglobulinemia
• Combined severe immunodeficiency syndrome
• HIV/AIDS
• IgA deficiency

Just because your levels are low or high doesn't mean you have an immune disorder; your healthcare provider may run some other tests to reach the definitive diagnosis. You should contact your consultant if you have any queries regarding your test results.

Related Tests:

• Serum electrophoresis
• Urine electrophoresis
• Immunofixation
• Serum complement levels
• Serum-free light chain testing
• Serum total protein