Rubella (also called German measles or 3-day measles) is an illness caused by a virus. Generally, infection causes no symptoms or a mild illness with a skin rash, swollen glands, and a low fever. However, if a woman gets rubella during her first 3 months of pregnancy, the illness can cause a miscarriage, severe birth defects (such as heart defects, deafness, cataracts, and mental retardation), or a stillborn baby. The earlier the infection occurs in a woman's pregnancy, the greater the risks to her antibodies in the blood that are produced by the immune system to help kill the virus. Once produced, the antibodies remain in the bloodstream for years. Their presence indicates that the person has an infection, has been infected in the past, or has been vaccinated against the disease. A rubella test is usually done for a woman who is or wants to become pregnant to determine if she has had rubella.

This test is done on a blood sample taken from a vein.

Rubella Test
Results

The results of a rubella test may be given in titers. A titer is a measure of how much the blood sample can be diluted before the antibodies against the rubella virus can not be detected any longer.

A titer of 1 to 8 (1:8) means that antibodies can be detected when 1 part of the blood sample is diluted by up to 8 parts of a salt solution (saline). A larger second number means there are more antibodies in the blood. Therefore, a titer of 1 to 32 indicates more rubella antibodies in the blood than a titer of 1 to 8.

A titer higher than 1 to 10 (such as 1:16 or 1:32) usually indicates that a woman is protected against rubella.

An initial rubella test may be done when a person first has symptoms of rubella (such as a mild rash, swollen glands, and a slight fever). A second rubella test may then be done when the person recovers. If titer levels in the second sample are four or more times greater than the first sample, a diagnosis of a recent rubella infection is confirmed.

A titer of 1 to 8 (1:8) in an infant 6 months or older indicates that he or she was infected with the rubella virus during the mother's pregnancy (congenital rubella).