To determine if you have had a recent or past infection with the rubella virus, or to check that you are protected from the rubella virus
A blood sample taken from a vein in the arm (this may need to be repeated after 7 days), oral fluid, a throat swab, or other more invasive samples such as amniotic fluid depending on symptoms.
Rubella is a viral infection that causes a fine red rash and flu-like symptoms, such as a high temperature, headache and a general feeling of being unwell. The raised red rash appears first on the face and neck and travels to the body and limbs. Teenagers and adults may experience more severe symptoms, such as joint pains, which may last several weeks. Rubella is usually harmless and the patient gets better without any special treatment, but when a woman gets rubella in the first three months of her pregnancy, serious birth defects, miscarriage, or stillbirth may result.
You may be infected when you come into contact with the nasal or throat secretions of someone who has an active viral infection. If you catch rubella, you are infectious one week before the rash appears and one week after. In children, rubella infections generally produce mild symptoms. The number of new cases of rubella is low in the UK since a combined vaccine for measles, mumps, and rubella (MMR) is recommended for all children.
How is the sample collected for testing?
Blood is taken by needle from a vein in the arm. Oral secretions or a throat swab is taken into a sterile container.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
A blood test can determine if you have had a recent or past infection, or if you have never been exposed to the rubella virus. People with recent infection will have a positive IgM antibody and those with a past infection (and those who have been vaccinated for rubella) will have a positive IgG antibody, while neither antibody will be present if there has been no contact with the virus. A blood test for IgG antibody will help the doctor predict if you are protected from infection or if you are at risk.
When is it requested?
If you are pregnant and have a rash and other symptoms of rubella, your doctor will request a laboratory test to help make the diagnosis since you cannot diagnose rubella just from your clinical appearance (other infections may look the same). Rubella infection during the first 16 weeks of pregnancy presents major risks for the unborn baby. Antibody testing is strongly suggested for women before they become pregnant so those who are not immune to the virus can be vaccinated before they conceive. Antibody testing is also offered at the first ante-natal visit. Antibody testing is often performed in infants born with abnormalities, such as deafness, mental retardation, heart defects, and cataracts that may have resulted from a rubella infection acquired before their birth. Direct tests to detect the presence of the rubella virus may be carried out on oral secretion or urine.
Testing for rubella antibody is not usually done on children or adults who were vaccinated to prove the vaccine was effective.
What does the test result mean?
In an adult or child, the absence of IgG antibodies to rubella means the person is unprotected. Absence of IgM antibodies and presence of IgG antibodies indicates a history of past exposure to the virus or vaccination. In an infant the presence of IgM antibodies means the baby was infected during the pregnancy.
Oral secretions or a throat swab are tested by a different technique looking for the presence of the rubella virus, not the body’s response to infection.
Is there anything else I should know?
Should pregnant women be vaccinated for rubella?
Does the vaccine have any risks?
The vaccine contains a live virus that has been altered so it cannot cause all the problems associated with a natural infection. Some people may have a rash that lasts 2–3 weeks after vaccination, and pain in their joints, especially their hands and wrists. Side effects are rarely seen in young children who get the vaccine.
What is the treatment for rubella in someone who has not been vaccinated?
There is no antibiotic or anti-viral drug that can prevent or "cure" the infection or reduce the risk of rubella to an unborn baby.
How soon after I have been exposed to the virus will I get rubella?
If you are going to have symptoms, the rash usually begins 15–17 days after coming in contact with an infectious person, but it may take as long as 3 weeks