Cytomegalovirus – Serology
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This page provides serological testing information for Cytomegalovirus (CMV) at Public Health Ontario (PHO). For information regarding other testing options, refer to Cytomegalovirus – Detection – Real Time PCR.
CMV serology is most often indicated for the diagnosis of acute/recent CMV infection, to determine evidence of past (latent) infection, and in the work-up of infants with suspected congenital infection.
When CMV infection is suspected in a pregnant woman and suspected congenital CMV in a newborn infant, order CMV serology and submit a urine for CMV PCR testing. On the PHO requisition form, be sure to request both CMV IgM and IgG. Include all relevant clinical information (e.g. pregnant, suspected congenital infection, etc.), onset date and signs and symptoms.
Donor testing is not available through PHO’s laboratory. Specimens from patients being screened as potential donors (e.g. organ, tissue, cells, fertility, etc.) should be referred to a laboratory that performs donor screening assays. Specimens received for donor screening at PHO’s laboratory will be rejected.
CMV IgG and/or CMV IgM
Blood, clotted – vacutainer tubes (SST)
CMV IgG and/or CMV IgM
Blood, clotted – vacutainer tubes (SST)
Submission and Collection Notes
Complete all fields of the requisition form, including:
- Test(s) requests and indications for testing
- Patient setting, specimen type and source
- Patient clinical history, vaccination history, signs and symptoms
Label the specimen container(s) with the patient’s first and last name, date of collection, and one other unique identifier such as the patient’s date of birth or Health Card Number. For additional information see: Criteria for Acceptance of Patient Specimens. Failure to provide this information may result in rejection or testing delay.
CMV IgG testing will be performed on all requests for CMV immunity serology.
CMV 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.
This information assists in providing the correct interpretation of results.
Timing of Specimen Collection
Acute: Collect the acute specimen within 7 days after the onset of symptoms.
Convalescent: Collect the convalescent specimen 7 to 10 days after the acute phase.
Haemolyzed, icteric, lipemic or microbially contaminated sera or plasma are not recommended for testing.
Please be aware that the assay used for the detection of CMV IgG & IgM has not been validated for screening potential donors including organs, tissues, cells, bone, corneas, fertility, etc. using serum or plasma samples.
- Bone marrow donor and Living Related donor who are otherwise healthy people will be tested.
- Transplant Recipient and Pre-Transplant Recipient work up assessment will be tested.
Storage and Transport
Centrifuge if using SST. Place specimen in biohazard bag and seal. Specimens should be stored at 2-8°C following collection and shipped to the PHO’s laboratory on ice packs as soon as possible.
All clinical specimens must be shipped in accordance to the Transportation of Dangerous Good Act.
Test Frequency and Turnaround Time (TAT)
CMV Diagnostic IgM and IgG serology is performed daily Monday to Saturday. TAT is up to 5 business days from receipt at the PHO’s laboratory.
The CMV IgG and IgM tests are performed using Chemiluminescent Immunoassay (CLIA) technology on the Diasorin LIAISON® XL for the qualitative determination of IgG and IgM antibodies to human cytomegalovirus (hCMV) in human serum.
The LIAISON® CMV IgG assay is intended to be used as an aid in the determination of serological status to CMV.
The LIAISON® CMV IgM assay is intended to be used as an aid in the diagnosis of acute CMV infection.
Test results are reported qualitatively together with a clinical interpretation based on the status of both IgM and IgG.
After a primary infection, both IgM and IgG antibodies develop within approximately 3-7 days after onset of symptoms. Both antibodies subsequently increase reaching a plateau 2-3 weeks later.
The presence of IgG antibody (in asymptomatic persons) provides evidence of past infection and therefore indicates evidence of latent infection and immunity to re-infection.
In symptomatic patients, indeterminate levels of antibody may indicate rising antibody levels following acute/recent infection. In asymptomatic patients indeterminate levels of antibody may be due to genuinely low levels of IgG antibody many years after the initial infection.
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 IgM and IgG antibodies may be observed in the early acute stage of infection. The levels will increase to reactive levels in subsequent weeks.
In the absence of acute/recent infection, indeterminate levels of IgG may represent very low levels of antibody many years after the initial infection whereas indeterminate levels of IgM may be due to declining levels of IgM several months post infection or occasionally as a result of assay non-specificity. In some patients persisting low levels of CMV IgM have been observed many months (> 6 months) after primary infection.
Assays for IgM antibody lack specificity for primary infection due to false-positive results, because of persistent IgM for months after primary infection, and because IgM may be positive in reactivated CMV infections.
If the acute blood sample shows a low reactive, indeterminate or non-reactive IgG and/or IgM result, a convalescent sample should be collected at least 10 to 14 days later. Recent infection is confirmed if a significant rise in antibody levels is observed between acute and convalescent sera.