A rubella titer is a blood test performed to check for antibodies to rubella, the virus responsible for causing the condition known as rubella or German measles. This test can be ordered in suspected cases of rubella infection, or if there is concern about a patient’s immunity status, most commonly in the case of women who are pregnant or preparing to become pregnant, as there are significant risks involved with having rubella in pregnancy. The test requires a small sample of blood sent out for laboratory analysis, and the length of time required for results varies.
In a rubella titer, the blood will be tested for the presence of antibodies associated with rubella exposure or infection. Two different antibodies are looked for: immunoglobulin G (IgG) and immunoglobulin M (IgM). The presence of both antibodies in the blood is evidence of recent infection. IgG antibodies alone are suggestive of immunity, depending on how concentrated they are. In newborns, IgM antibodies alone indicate that the newborn was exposed in utero, and may have health problems like hearing loss.
If the levels of IgG antibodies in a rubella titer are high enough, the patient is immune and does not need any treatment. A laboratory may also return a negative result, indicating no protection from the virus, or an irregular or uncertain result, where there are some antibodies present, but not enough to confirm immunity. These patients need another rubella immunization to protect them from infection. If a woman is already pregnant, she cannot receive a vaccination until after the delivery, and will need to be careful about avoiding people who carry the virus. Thanks to widespread rubella vaccination, herd immunity usually provides protection for pregnant women who might be susceptible.
The rubella titer can be ordered for health care workers and students preparing for school, as well as pregnant women. These individuals are at higher risk of contracting rubella because of their close contact with patients and the crowded conditions, respectively. If the test reveals inadequate protection, another vaccination can be given.
People can also request titers if their immunization records have been lost and they want to confirm that they have been vaccinated; the other option is to get another vaccination. Being vaccinated while already protected is not harmful and may be easier and more cost effective than getting a rubella titer. Titers are also available to check for immunity to other common diseases, for people concerned about whether vaccines were effective.