Rubella (German Measles) - Exams and Tests

Exams and Tests

A rubella blood test identifies antibodies to the rubella virus in a sample of blood. This information can help a doctor determine:

• Whether a recent infection was caused by the rubella virus.
• Whether you have been vaccinated against rubella or are otherwise immune to the virus.

Sometimes, a viral culture may also be used to determine whether a current infection is caused by the rubella virus. However, the results from this test may not be available for several weeks.

For children and adults

If you or your child have not been immunized and your health professional suspects rubella, a blood test for rubella antibodies should be done to confirm the diagnosis.

Rubella may be diagnosed without testing if you have not been immunized. This can occur if you develop typical symptoms after being exposed to someone with a confirmed case of rubella infection.

For pregnant women

As part of your prenatal care, your doctor may want you to have a blood test to find out if you have had rubella or the vaccine. (Your body will make antibodies if you have had the disease or the vaccine.) If your body has made antibodies, you have immunity.

If your body does not have antibodies, you are not immune. This means if you were exposed to rubella, you could get the disease and pass it on to your baby. You can help prevent rubella by avoiding close contact with people infected with the virus.

If you are not immune and have been around people who have rubella, your doctor will use the blood test to see if you have antibodies to fight the disease.

• If antibodies are not found, the test is negative. This means you are not immune to the disease. Your doctor may order immune globulin (IG) for you. Immune globulin does not prevent rubella infection, but it may reduce your symptoms and reduce the chance of birth defects.
• If antibodies are found, the test is positive. This means you are immune to rubella. To be safe, the blood test may be repeated again in 6 weeks.

For newborns

An infant born with defects that suggest congenital rubella syndrome (CRS) should be evaluated immediately to determine whether rubella is the cause. Diagnosis of a newborn with CRS is based upon the newborn's physical exam and the mother's medical history, including prenatal care records. If CRS is diagnosed, measures are taken to prevent the transmission of the virus to others who are in the hospital.

Some states test every newborn for hearing impairment, the most common birth defect related to rubella. If a problem is found, the infant is usually further tested for rubella.² This helps doctors know whether they should look for other birth defects and signs of CRS.