Rubella Ab

Keywords: Rubella antibody, Rubella serology

Specimen:

5-10 mL blood in plain tube.

An acute phase sample should be taken within a few days of onset of the rash; convalescent (after 10-14 days) samples may also be required for interpretation.

Method:

EIA.

Application:

To support a clinical diagnosis of rubella (German measles); determination of immune status, especially before or during pregnancy, and after vaccination.

Diagnosis of congenital infection.

Interpretation:

An IgG level of > 10 in a well adult, is indicative or previous infection or vaccination.

IgM antibody is usually positive by 5 days after onset of the illness and will become undetectable after 8 weeks.

A four-fold rise in IgG titre between acute and convalescent samples indicates recent infection.

IgM antibodies in maternal serum indicate high fetal risk, particularly in the first and second trimester. However, cross-reactions may occur with eg, parvovirus infection. Confirmation of primary infection may require determination of IgG avidity index.

In congenital rubella, IgM becomes positive within one month of birth and is usually negative by twelve months. Rising IgG titres are seen until about nine months of age.

Reference:

Bellini WJ and Icenogle JP. In: Murray PR et al eds. Manual of Clinical Microbiology. 8th ed. 2003. ASM Press.