Also known as:
Name: Rubella IgG/IgM antibodies
Related tests: HIV antibodies, TORCH
Why is the test done?
To check whether you have adequate antibody protection against rubella infection. To check for a recent or past infection.
When is it done?
Before or early in pregnancy, to check antibody protection; in a pregnant woman with symptoms of rubella, fever and rash; in a newborn baby who has developed abnormally or has signs at birth that could be due to an infection in the womb; and whenever a recent infection needs to be checked for or immune status needs to be confirmed.
What samples are required?
A blood sample is taken from a vein in the arm in adults, or from the heel or the umbilical cord in newborns.
What is being analysed?
The test detects and measures rubella antibodies in the blood. Antibodies are proteins that the body produces in response to infection or exposure to a microorganism or foreign agent. Rubella antibodies are produced in response to infection with the rubella virus. Two types of antibodies are produced, IgM and IgG, responsible for short-term and long-term protection respectively. IgM antibodies are the first to appear in the blood after contact with the virus, peak between the seventh and tenth day after infection and then start to decline over the following weeks, except in newborns, in whom they can persist for months after birth, up to one year of age. IgG antibodies appear later than IgM, but once produced they remain in the circulation for life, giving the body permanent protection against any subsequent rubella reinfection. The presence of specific IgM antibodies in the blood indicates a recent rubella infection, while the presence of specific IgG indicates either a past infection or that the person has been vaccinated against rubella, measles and mumps and that the vaccine has worked.
The rubella virus causes a rash that is always very mild, made up of very small red spots that appear first on the face and neck, then on the rest of the body, and disappear within a few days. The virus is spread through nose and throat secretions and can cause symptoms such as fever, swollen lymph nodes, a red nose and eyes, and joint pain. The symptoms can be so mild, especially in children, that they are not recognised as a viral infection. In most cases rubella clears up within a couple of days without any particular medical treatment and causes no later health problems. The main concern is women who catch rubella in the first three months of pregnancy: the developing fetus is very vulnerable if exposed to the virus, and the infection can cause miscarriage, stillbirth and/or congenital rubella syndrome (CRS), a set of serious lifelong birth defects. CRS can cause developmental delay, intellectual disability, deafness, microcephaly, liver disease and heart disease.
How is the sample collected for testing?
A blood sample is taken from a vein in the arm in adults, or from the heel or the umbilical cord in newborns.
How is it used?
When is it requested?
What does the test result mean?
What else should I know?
How is it used?
The rubella antibody test is requested to check for adequate protection against the virus and to detect a recent or past infection. The test also identifies people who have never been in contact with the virus and/or have not been vaccinated. The IgG test is prescribed for all pregnant women and for those planning a pregnancy soon, to check that they have enough rubella antibodies (antibody titre) to protect them against infection during pregnancy.
The specific IgG and IgM test may be requested by the doctor if a patient, whether pregnant or not, has symptoms typical of rubella infection. The test may also be requested for a newborn baby who may have been infected during pregnancy or who has birth defects that could be due to rubella infection.
In other cases, the test is requested to certify protection against the virus, which may be required at work, for healthcare workers, for people being admitted to a college or, in some countries, together with other blood tests, to obtain a marriage licence.
When is it requested?
The rubella IgG test is prescribed during pregnancy or when a pregnancy is being planned, and whenever immune status against the infection needs to be checked. The specific IgM and IgG test is prescribed when a pregnant woman has symptoms typical of the infection, such as fever and rash, or other symptoms, to make a differential diagnosis from other conditions that cause similar symptoms.
Both immunoglobulins are also tested in newborn babies whose mother caught the infection during pregnancy or who have birth defects that could be due to congenital rubella syndrome (deafness, cataracts, cardiovascular and central nervous system abnormalities).
To detect and “date” a recent infection, two blood samples may need to be taken two to three weeks apart: the first may be negative and the second positive or, conversely, the second may show a lower antibody titre than the first.
What does the test result mean?
The absence of rubella IgG antibodies in a child or adult indicates that there has been no contact with the virus and no vaccination, and therefore no protection against the virus. The presence of specific IgG but not IgM indicates either vaccination or past exposure to the virus and, in either case, adequate antiviral protection. The presence of specific IgG but not IgM in a newborn baby indicates that maternal antibodies passed to the fetus during pregnancy and that the baby is protected against infection for the first six months of life. The presence of specific IgM in a newborn baby indicates that an infection occurred in the womb, as maternal IgM does not pass to the fetus through the placenta. The presence of specific IgM, with or without IgG, indicates a recent rubella infection.
Rarely, false-positive results may occur for specific IgM because of cross-reaction between test components and proteins in the circulation. To confirm the result, the doctor may request two specific IgG tests two to three weeks apart to check for a rise in antibody titre following a possible recent infection.
Is there anything else I should know?
The rubella virus can be looked for by analysing its genetic material or by viral culture, using an alternative biological sample such as a throat swab. The virus takes at least a week to grow in culture, and molecular tests or specific antibodies are needed to confirm its presence. This procedure may be useful in some cases for diagnosing infection in newborns. Because this procedure is complex and expensive, many laboratories rely on a reference laboratory, such as the US Centers for Disease Control and Prevention (CDC). The CDC also monitors the number of cases of rubella and congenital rubella syndrome to check the effectiveness of the vaccine in use and to detect any outbreaks.
1. Should pregnant women be vaccinated against rubella?
2. Does the rubella vaccine carry any risks?
3. How long does it take from contact with the rubella virus to the development of the disease?
4. What does the abbreviation MMR on the vaccine stand for?
1. Should pregnant women be vaccinated against rubella?
The vaccine must not be given to pregnant women, and a woman who has been vaccinated against rubella should wait at least one month before becoming pregnant.
2. Does the rubella vaccine carry any risks?
The vaccine contains a live virus that has been weakened so that it produces an immune response without causing infection. Some people may have a rash and joint pain (especially in the hands and wrists) for two to three weeks after vaccination. Side effects are rare in young children who are vaccinated. Immunocompromised patients, such as people with AIDS or those receiving chemotherapy for cancer, should consult their specialist before being vaccinated.
3. How long does it take from contact with the rubella virus to the development of the disease?
The first symptoms, such as the rash, appear about 15-17 days after contact with an infected person, but in some cases it can take up to three weeks. A person who has caught the infection is in turn infectious from one week before the rash appears until one or two weeks afterwards. A baby infected in the womb can remain infectious for months after birth.
4. What does the abbreviation MMR on the vaccine stand for?
Measles, mumps and rubella. All three antigens are contained in a single vaccine because the three microorganisms cause common viral diseases.