Rubella Antibodies, IgM

Laboratory assay overview

Rubella (German Measles) is a common and usually benign viral infection of children. IgM antibody is detectable 11-25 days after the onset of exanthem, in most individuals 15-25 days after vaccination, and in 90-97% of infants with congenital rubella between 2 weeks and 3 months after birth. Acute and convalescent IgG titers may be interpreted to identify a >30% rise in the antibody index. A positive IgG antibody indicates successful immunization or past exposure.

Laboratory assay overview

For the in vitro detection of IgM antibodies specific for rubella. IgM antibodies are associated with acute viral infections. IgM detection is useful in the following situations: evidence of infection can be obtained from only one acute phase specimen if the IgM results are positive; the IgM test can also be used to differentiate between primary infection and re-exposure. Rubella-specific IgM is found in virtually all infected patients by three weeks postdevelopment of a rash. Rubella-specific IgM is also found in 80% of postvaccination patients by three weeks. Congenitally infected infants will show an IgM response at 2 to 12 weeks postnatally.

Laboratory assay overview

Rubella is an acute exanthematous viral infection of children and adults. Rash, fever and lymphadenopathy characterize the illness. While many infections are subclinical, this virus has the potential to cause fetal infection with resultant birth defects. In the absence of a current or recent infection, a demonstration of specific IgG on a serum sample is evidence of immunity to rubella. A positive rubella IgM result does not necessarily indicate current or recent infection. Without a history of exposure to rubella or symptoms consistent with rubella, the IgM result may be difficult to interpret. Rubella IgM can be false positive due to other causes (e.g., parvovirus, rheumatoid factor, cytomegalovirus). Rubella IgM may also persist for more than 12 months after vaccination or natural infection. For a serologic diagnosis of congenital rubella in the neonatal period, antibody to rubella virus should be measured in both infant and maternal sera. If IgM is detected in a newborn infants serum, it is probable that transplacental rubella infection has occurred.

Quest Diagnostics population reference ranges

Quest Diagnostics calculates these statistical intervals for this specific assay and demographic group, not as universal optimal targets.