What are the other Names for this Test? (Equivalent Terms)
- Immunoglobulin Tests
What is Antibody Test? (Background Information)
- Antibodies or immunoglobulins are proteins produced by the body’s immune system in response to provoking substances, called antigens. This antigen is usually a bacteria/virus/fungi, or even a worm
- However, in some instances, the immune system fails to recognize the body’s own tissues and starts producing antibodies against them. These antibodies, termed as autoantibodies, damage the body’s own tissues (damage of “self-tissue”), leading to a group of diseases, called autoimmune disorders
- Antibodies may also be produced against foreign antigens, which are from other individuals, such as occurring during a blood transfusion, or an organ transplant
- The term Antibody Tests, broadly refers to tests that may either detect the presence or absence of particular antibodies (qualitative), or estimate the amount of antibody present (quantitative)
- Immunoglobulin types include IgM, IgG, IgE, IgA, and IgD. The ones that are used for testing are mainly IgM and IgG. IgE and IgA may also be tested, under some circumstances
- A particular antibody can react only with a particular antigen. This specificity forms the basis for all Antibody Tests. These investigations seek specific antibodies in the test samples (usually in blood), by mixing them with particular antigens and examining the antigen-antibody complex formations
- IgM and IgG are antibodies produced in response to infections, by some microorganisms. IgM is the initially antibody produced, while IgG production occurs much later. Detecting these antibodies in blood, helps in diagnosing infections; the type of antibody, is also an indicator of the time since infection, in some cases
- IgE antibody is produced during an allergic response and is used to test for allergy to specific substances. IgA may also be used for allergy testing, and to diagnose a condition, called celiac disease (in which there is an increased sensitivity to gluten in food, leading to digestive tract disturbances, after consuming wheat-based food)
What are the Clinical Indications for performing the Antibody Tests?
Antibody Tests may be ordered under the following circumstances:
- To diagnose infections
- To find out the immune status after vaccination - the antibody levels are measured
- To diagnose autoimmune conditions, allergies to specific substances
- To examine the cause for rejection of transplanted organs, or adverse reactions following blood transfusions
- Serial antibody measurements help in monitoring the course of infectious disease and autoimmune conditions
How is the Specimen Collected for Antibody Tests?
Sample required: Blood
Process: Blood sample is drawn through a needle inserted into the vein (arm).
Preparation required: None
What is the Significance of the Antibody Test Result?
The result of an Antibody Test maybe as follows:
- The antibody may be reported to be “detected” or “not detected”, depending on the presence or absence of the specific immunoglobulin that is being tested for
- When immune status is being evaluated, the result may read as either “immune” or “non-immune”, depending on how adequate the antibody levels are. The result may also report the levels of antibody, as being above a particular cut-off value if immune, or the antibody concentration may be reported as a numerical value
- A positive antibody is evaluated using titers (the sample is diluted and serial dilutions, from highest to lowest concentrations, are tested). Antibody titers show whether a positive antibody level is significant, or not
- IgM antibodies denote recent antigen exposure, while IgG antibody detection indicates that the exposure occurred much earlier
The laboratory test results are NOT to be interpreted as results of a "stand-alone" test. The test results have to be interpreted after correlating with suitable clinical findings and additional supplemental tests/information. Your healthcare providers will explain the meaning of your tests results, based on the overall clinical scenario.
Additional and Relevant Useful Information:
Certain medications that you may be currently taking may influence the outcome of the test. Hence, it is important to inform your healthcare provider, the complete list of medications (including any herbal supplements) you are currently taking. This will help the healthcare provider interpret your test results more accurately and avoid unnecessary chances of a misdiagnosis.