Titer

A titer is an expression of a substance’s concentration or the strength of a solution. In medicine, it is the measurement of specific disease antibodies that are present in the patient's blood.

For instance, expectant mothers are sometimes tested for rubella antibodies since this is a disease that shows few obvious symptoms (a person may even be unaware of ever having had it) and can damage a fetus if contracted during pregnancy. Moreover, antibody titers can identify if individuals are already immune to certain illnesses and blood titers may help specify medical treatment. Such measurements are often expressed in ration form. For example, a titer increase from 1:1 to 1:5 specifies a re-infection.