Rubella – Serology

Testing Indications

Testing for Rubella immunity is indicated during pre-natal evaluation of pregnant women, to determine response post-vaccination, and for pre-employment screening (e.g. healthcare workers).

When Rubella (German Measles) infection is suspected-Contact your local Public Health Laboratory to ensure that appropriate testing is being requested and also contact your local Public Health Unit to inform them of all possible or suspect cases of rubella.

When Rubella infection is suspected, in addition to collection of serology samples, also collect and submit samples for the detection of Rubella virus by RT-PCR. Refer to the test information sheet Rubella – Diagnostic RT-PCR for specimen collection and testing information.

Specimen Collection and Handling

Specimen Requirements

Test Requested Required Requisition(s) Specimen Type Minimum Volume Collection Kit

Rubella Immunity

Whole blood or serum

5ml Blood or 1.0 ml serum

Blood, clotted-Vacutainer tubes (SST)

Rubella Diagnosis

Whole blood or serum

5ml Blood or 1.0 ml serum

Blood, clotted-Vacutainer tubes (SST)

Submission and Collection Notes

1

Rubella IgG testing will be performed on all requests for Rubella immunity serology.

2

Rubella IgG and IgM testing will be performed on diagnostic requests only when the following clinical information is provided on the General Test Requisition Form indicating acute/recent infection, vaccination history, relevant signs, symptoms, and/or clinical history, and onset date.

Timing of Specimen Collection

Acute: Collect the acute sample within 7 days after the onset of the rash.

Convalescent: Collect the convalescent sample 7 to 10 days after the acute.

Limitations

Hemolysis, icteric, Lipemic or microbial contaminated serum is not recommended for testing.

Preparation Prior to Transport

Label the specimen container with the patient’s full name, date of collection and one other unique identifier such as the patient’s date of birth or Health Card Number. Failure to provide this information may result in rejection or testing delay.

Centrifuge if using SST. Place specimen in biohazard bag and seal. Specimens should be stored at 2-8°C following collection.

Specimens more than 10 days post collection will not be tested.

 

Special Instructions

Centrifuge if using SST. Place specimen in biohazard bag and seal. Specimens should be stored at 2-8°C following collection and shipped to PHO Laboratory on ice packs.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

Rubella serology to detect Rubella IgG and IgM is performed daily Monday to Friday.

Turnaround time is up to 5 days from receipt by PHO Laboratory.

Reporting

Results are reported to the ordering physician or health care provider as indicated on the requisition.

Specimens that are positive (reactive) for Mumps IgM are also reported to the appropriate Medical Officer of Health as per Health Protection and Promotion Act.

Test Methods

Rubella IgG Immunity (Request for Prenatal Screening)

Specimens for Rubella IgG (Immune status) are tested using a Chemiluminescent micro particle immunoassay (CMIA) for the qualitative detection of human IgG antibody to Rubella virus. Results are reported as Qualitative

Rubella IgG Immunity (Request for Post-vaccination screening, Pre-employment screening e.g Healthcare workers)

The Rubella IgG (Immunity) tests are performed using the BioPlex 2200 MMRV IgG kit for use with the Bio-Rad BioPlex 2200 System. It is a Multiplex Flow Immunoassay test intended for the qualitative detection of IgG antibodies to rubella virus in human serum.
Results are reported as Qualitative

Rubella IgG and IgM Diagnostic

The Rubella IgG (Diagnostic) tests are performed using the LIAISON® Rubella IgG II assay. It uses chemiluminescent immunoassay (CLIA) technology for the quantitative determination and qualitative detection of specific IgG antibodies to rubella virus in human serum. The assay is intended to determine the immunological status of individuals, including previously vaccinated subjects, and as an aid in the diagnosis of active or past Rubella virus infection. The test has to be performed on the LIAISON® Analyzer family.

The Rubella IgM (Diagnostic) tests are performed using the LIAISON® Rubella IgM assay. It uses chemiluminescent immunoassay (CLIA) technology on the LIAISON® Analyzer family for the qualitative determination of IgM antibodies to rubella virus in human serum samples. It is intended for use as an aid in the diagnosis of a current or recent Rubella infection in individuals with signs and symptoms of Rubella, or suspected of having rubella virus infection, including women of child bearing age.

Test results are reported qualitatively together with a clinical interpretation based on the status of both IgG and IgM.

Interpretation

A positive result for Rubella IgG antibodies indicates immunity to rubella virus as a result of recovery following past infection or immunization.

After a primary infection, both IgG and IgM antibodies develop within 3-7 days after rash onset. Both antibodies then increase reaching a plateau 2-3 weeks later.

Antibody levels may be reported as Non-Reactive (no detectable antibody), Indeterminate (the level of antibody detected is considered borderline reactive or equivocal) or Reactive (antibody is detectable within the positive range of the assay). 

Non-Reactive and Indeterminate levels of   both IgG and IgM antibodies may be observed in the acute stage of infection rising to reactive levels in subsequent weeks. 
In the absence of acute infection, indeterminate levels of IgG may represent very low levels of antibody many years after initial infection or vaccination whereas indeterminate levels of IgM may be due to declining levels of IgM several months post infection or possibly due to assay non-specificity.

If the acute blood sample shows low reactive, indeterminate or non-reactive IgG and/or IgM results then a convalescent sample should be collected. Recent infection is confirmed if a significant rise in antibody levels is observed between acute and convalescent sera.

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Updated 14 Oct 2020