Immunoglobulin G Test - IgG

Immunoglobulins G Immunoassay Blood test helps to check whether an individual is having normal or abnormal levels of IgG in the blood. The immune system of our body protects us from bacteria, viruses, and other microorganisms. In response to these disease-causing organisms, our immune system produces specific proteins called immunoglobulins. These immunoglobulins protect us from infection. The test, which measures the amount of Ig proteins in the blood, saliva, or cerebrospinal fluid (CSF) (fluid surrounded by the brain and spinal cord) is Immunoglobulin G (IgG) test. When disease-causing microorganisms or foreign substances (also known as antigens) infect a person, our immune system recognises it. The immune system cells produce specific immunoglobulins (also called antibodies) against the antigens. When the same infection re-occurs, our body remembers it and produces more antibodies rapidly to prevent the re-infection. Our immune system produces five types of immunoglobulins: Immunoglobulin M (IgM) Immunoglobulin G (IgG) Immunoglobulin A (IgA) Immunoglobulin D (IgD) Immunoglobulin E (IgE) Immunoglobulin G (IgG) is the most common type of antibody present in the body. It is found in all body fluids and comprises 70-80% of all immunoglobulins present in the body. IgG provides long-term protection against infection. They memorise the microorganisms and develop specific antibodies against them. They also prevent the recurrence of the infection. It is the only immunoglobulin that can pass from mother to baby through the placenta during pregnancy. IgG from the mother protects the baby in the first few months after birth. There are four subclasses of IgG: IgG1 IgG2 IgG3 IgG4. The immunoglobulin test measures the amount of each Ig: IgA, IgM, and IgG. Separate testing is done to measure the subclasses of IgG. If the levels of Ig are low or high, it may indicate the presence of some health problem. The test shows whether the immune system of our body is working correctly. If the level is low, the immune response is low, and there are more chances of getting an infection. A high level means the immune response is overactive, and you could have allergies. Symptoms for deficiency or excess of IgG differ greatly. There may be frequent infections, fever, skin rashes, sinus infection, diarrhoea, allergies, or a lung infection. The IgG test is also prescribed if you have a family history of immunodeficiency. It can detect bacterial infections, low immunity, autoimmune disorders, cancers like multiple myeloma, and also infections in newborns. IgG tests are easily available in India. Recently, during the COVID-19 pandemic, the antibody IgG test was used to determine the presence or absence of antibodies after the infection and vaccination. IgG antibodies usually become positive after 8 - 13 days of infection & peak around 21 days. The test is not used to diagnose the active infection though.