Measles – Serology

Testing Indications

Serology for Measles Immunity Serology (Measles IgG) may be indicated to determine immune status (either following natural infection or post-vaccination).

Unknown Immunization Status: Immunization vs. Serology

If a patient’s immunization records are unavailable, immunization with measles-containing vaccine is preferred, rather than ordering serology to determine immune status. This avoids the potential for false positive results, reduces the risk of missed opportunities for immunization and is consistent with advice from the CIG. Please note this does not apply to specific occupational groups such as healthcare workers who require either documentation of immunization or serologic proof of immunity.

When Measles infection is suspected - Contact Public Health Ontario 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 measles.

Diagnosis for symptomatic patients or post exposure, requires additional samples for testing by PCR, refer to the test information sheet Measles-Diagnostic PCR for specimen collection and testing information.

Specimen Collection and Handling

Specimen Requirements

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

Measles Immunity

Whole blood, serum, or plasma

5.0 ml blood

1.0 ml serum or plasma

Blood, clotted - vacutainer tubes (SST), or Lavender top (EDTA) tube

Measles Diagnosis

Whole blood, serum, or plasma

5.0 ml blood

1.0 ml serum or plasma

Blood, clotted - vacutainer tubes (SST), or Lavender top (EDTA) tube

Submission and Collection Notes

1

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

2

Measles 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

Hemolysed, icteric, lipemic or microbially contaminated sera or plasma are 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.

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 Public Health Ontario Laboratory on ice packs.

Requisitions and Kit Ordering

Test Frequency and Turnaround Time (TAT)

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

Turnaround time for test results is up to 5 days from receipt by PHO laboratory.

Reporting

Measles IgG is a qualititative test. Quantitative results will ONLY be provided when the reason for testing is for the determination of immunity / immune status and this is clearly indicated on the PHOL requisition. Measles IgG test results are reported both qualitatively (Non-Reactive, Indeterminate or Reactive) and quantitatively together with an interpretation of the patient’s immune status based on the level of measles IgG detected.

Measles IgG and IgM diagnosis serology is performed when requested along with clinical information indicating acute/recent infection, vaccination history, relevant signs, symptoms, and/or clinical history, and onset date. For diagnostics requests the IgG quantitative results will not be reported.

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

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

Test Methods

The Measles IgG and IgM tests are performed using ELISA (Enzyme Linked Immunosorbent Assay) test kits manufactured by Euroimmun (Germany). The IGG and IGM ELISA tests are both quantitative (IGG) and semi-quantitative (IGM) measuring human antibodies of the IgG and IgM classes against measles virus in serum or plasma.

Interpretation

The Measles IgG and IgM tests are performed using ELISA (Enzyme Linked Immunosorbent Assay) test kits manufactured by Euroimmun (Germany). The IGG and IGM ELISA tests are both quantitative (IGG) and semi-quantitative (IGM) measuring human antibodies of the IgG and IgM classes against measles virus in serum or plasma.

Qualitative Result Quantitative Result Interpretation
Non-reactive <200 mIU/ml No Evidence of Immunity.(Indicates susceptibility
Indeterminate ≥200 - <275 mIU/ml Antibody levels in the indeterminate range for this assay may be insufficient to confer immunity.
Reactive ≥275 mIU/ml Evidence of past infection / vaccination; evidence of immunity.

These interpretations assume the absence of acute or recent infection

After a primary infection, both IgG and IgM antibodies develop within 3-7days 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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Laboratory Services

customerservicecentre@oahpp.ca

Updated 12 June 2019