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Why Doctors Check IgG Levels With a Blood Test

written by: angiem1981•edited by: Diana Cooper•updated: 11/17/2010

The IgG blood test is ordered to determine the amount of immunoglobulin G in the blood stream. Although IgG is the most occurring immunoglobulin in the blood, the results can reveal the presence of infection and your level of immunity.

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    This is a simple blood test used to determine the amount of immunoglobulin G, an important part of the body’s immune system. This particular immunoglobulin is the most prevalent in the body and helps protect from bacteria and other pathogens that may cause illness by creating an antigen to fight off such pathogens. Following the first initial exposure to the agent, enough immunoglobulin G is created to fight off that particular type of infection in the future. This is the only immunoglobulin which is capable of crossing the placenta during pregnancy and is responsible for providing immunity to the newborn through the first months of life.

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    Why Might Your Physician Order this Test?

    There are a variety of different reasons why your physician may order an IgG blood test. First and foremost, levels of immunoglobulin in the blood can determine whether or not exposure to an illness has occurred. In addition to this, the IgG can also indicate the immune status of the patient following an illness or vaccination. For example, it is not uncommon for health care workers and health students to have this type of testing to identify the immunity status against Rubella and other illnesses commonly vaccinated for. Your physician may also order this test if you are experiencing chronic inflammation, recurring infection or when there is reason to believe that abnormalities in the immune system are caused by the IgG antibodies.

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    How is the Test Performed?

    The IgG blood test can be performed in almost any health care sitting by drawing a sample of blood. There are no special requirements prior to testing, such as fasting. Most medications will not interfere with testing. However, you should consult with your physician, as certain medications can affect the production of these antibodies. There are no side effects associated with this test, with the exception to those who suffer from bleeding disorders. In these cases, excessive bleeding is a rare complication.

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    How Are the Results Interpreted?

    The results of the IgG blood test are read as either high or low. Increased levels are commonly associated with an infection within the body. However, high amounts may also indicate autoimmune disorders, Cirrhosis and extreme reactions from exposure to other substances. Low levels of immunoglobulin G can also indicate potential problems, such as losses of protein from the body. These losses can be a result of either a disease process, such as diabetes or from trauma, such as burns. However, there are limitations to the IgG blood results. This test alone can not be utilized to diagnose a specific disease. In most cases, the IgG is ordered in combination with the IgA and IgM, along with other tests when the physician suspects a certain illness or condition.

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    Bibliography

    Immunoglobulins. WebMD. 18, August 2008. Viewed 15, November 2010. http://www.webmd.com/a-to-z-guides/immunoglobulins

    Quantitative Immunoglobulins. Lab Tests Online. Modified 9, November 2010. Viewed 15, November 2010. http://www.labtestsonline.org/understanding/analytes/immunoglobulins/glance.html

    Quantitative nephelometry. Medline Plus. 2, June 2010. Viewed 15, November 2010. http://www.nlm.nih.gov/medlineplus/ency/article/003545.htm