Why are antibody tests done?
The main reasons that antibody tests are done or antibody concentrations are measured are to:
- Document exposure to an infectious or foreign agent
- Evaluate protection level (immune status) against a particular microorganism
- Diagnose an autoimmune condition
- Diagnose the reason for a transfusion reaction or a rejection of a transplanted organ
- Diagnose an allergy
- Monitor the course of an infection or autoimmune process
There is not a single "umbrella" test that will measure all of a person’s various antibody levels; antibodies are as individual as the diseases they target. Antibody tests are ordered singly or in combinations, depending on a patient’s symptoms and on what information the doctor is trying to gather. If the doctor suspects a current infection, two samples (called acute and convalescent samples) may be collected (a few weeks apart) to look for changes in antibody levels.
Some antibody testing focuses on specific IgM, IgG, IgA and/or IgE tests. IgG and IgM tests are used primarily for diagnosis and monitoring of infectious diseases or for determination of immune status. IgE testing is used primarily to identify and monitor allergies to specific substances. IgA testing is often used in allergy testing and in the diagnosis of celiac disease.