What Is a Titer Test?

A “titer” is a ratio or measurement of how much antibody to a certain virus (or other antigen), expressed in numbers, and is circulating in the blood at that moment. Antibodies can fluctuate in concentration. A titer on one day can be different than the following day. Titers are usually expressed in a ratio, which is how many times a technician had to dilute the blood plasma before they couldn’t find antibodies anymore. The lab/technician dilutes it two times, and then can’t find any more antibodies; it would be expressed as a titer ratio of 1:2. Dilution fluid is generally doubled, so you will increase titers from 1:40, 1:80, 1:160, etc. If the lab dilutes the blood serum a thousand times before they can’t find any antibodies, this would equal a titer of 1:1000. The higher a titer, the most likely there is an autoimmune disease present or was presented.

antigen:antibodies

 

Titer of 1:8 on an indirect Coomb’s test [mixing the mother’s blood Rh-, with Rh+ RBCs (the antigen)] shows the mother’s body already has been sensitized, or has a memory, and will clump – producing antibodies. This test is done when the infant is still in uterus and indicates amniocentesis to determine severity of hemolytic anemia of infant, and bilirubin in amniotic fluid.

A titer on the newborn’s umbilicus cord blood, called a direct Coomb’s test is done at birth to type the infant’s blood and Rh status. This helps in knowing if there are any hemolytic disorders present such as Rh incompatibility or ABO incompatibility. If antibodies are present, (a measure of maternal sensitization) titers of 1:64 will indicate a need for exchange transfusion. Titers of

If the baby received the mother’s antigens, lysis of RBS will start and visibly seen by jaundice. Genetic testing gives the opportunity for isoimmunization and decreased the need for exchange transfusions.