An antibody titer is a measurement of the amount of antibodies present in a person's serum (blood). It is used to determine how well a person's immune system is responding to a particular antigen or pathogen. Antibody titers are commonly used to diagnose infectious diseases, such as measles, mumps, and rubella. The higher the antibody titer, the greater the chance that the person has been exposed to the pathogen or antigen and is producing an immune response.
An antibody titer test is performed by taking a sample of the patient's blood and measuring the levels of specific antibodies in it. This measurement is then compared to a standard or reference value. If the antibody titer is higher than the reference value, the person is considered to have been exposed to the antigen or pathogen. If the titer is lower than the reference value, the person is considered to have not been exposed.
Antibody titers are also used to measure the effectiveness of a vaccine. A vaccine stimulates the body's immune system to produce antibodies that are specific to a particular pathogen. By measuring the antibody titer after a vaccine has been administered, it can be determined if the vaccine has been effective in stimulating an immune response.
In summary, an antibody titer is a measurement of the levels of specific antibodies in a person's serum. It is used to diagnose infectious diseases and to measure the effectiveness of a vaccine. The higher the antibody titer, the greater the chance that the person has been exposed to a particular antigen or pathogen and has produced an immune response.