CMV IgG
<0.5 U/mL - all genders and ages >12 months
CMV IgM
Negative is considered a normal result (all genders and ages)
Uncertainty of measurement:
CMV IgG
TBD
CMV IgM
N/A
CMV IgG and IgM assays are tested for all patient CMV serology requests.
Testing is performed daily with automatic release of all results except when the CMV IgM assay is reactive.
C MV IgM reactive results require review which will occur within 48h.
CMV IgG
Effective from 30 September 2024
Assay: Elecsys CMV IgG (quantitative)
Method Principle: Sandwich assay principle using Electrochemiluminescence (ECLIA)
Platform: COBAS e801 Immunoassay module
CMV IgM
Effective from 30 September 2024
Assay: Elecsys CMV IgM (qualitative)
Method Principle: Mu (u) - capture assay principle using Electrochemiluminescence (ECLIA)
Platform: COBAS e801 Immunoassay module
Clinical
There are three clinical patient settings with respect to CMV infection as listed:-
Immunocompetent
CMV infection in immunocompetent individuals is usually asymptomatic. Symptomatic infection in immunocompetent hosts manifests as a mononucleosis-like syndrome (prolonged fever, myalgia, atypical lymphocytosis, mild hepatitis), although can cause severe disease (colitis, meningoencephalitis, haemolytic anaemia, thrombocytopenia, arterial or venous thrombosis, ocular complications, hepatitis, pneumonitis
Immunocompromised patients.
Patients with defects in cell-mediated immunity are more susceptible to CMV infection (solid organ transplant, haematopoietic stem cell transplant, HIV infected, recipients of chemotherapy, congenital immune deficiencies). CMV disease in immunocompromised patients may be due to primary infection, reactivation or re-infection. Symptoms vary in severity and site affected. Frequent manifestations include retinitis, colitis and pneumonitis, in addition to non-specific symptoms such as malaise, fever, myalgia, leukopenia, thrombocytopenia and mild hepatitis.
Congenital / Perinatal infection
Congenital CMV infection can occur as a result of maternal primary infection or reactivation. Congenital infections can have severe manifestations: intra-uterine growth retardation, jaundice, petechiae, myocarditis, pneumonitis, chorioretinitis, neurological symptoms and sequelae. Peri-partum infection can occur via exposure to the birth canal or breast milk. Urine and saliva are the most sensitive specimen types for the diagnosis of congenital / post-partum CMV in new-borns.
Serology
Serology results in the immunosuppressed patient and those patients receiving blood products should be interpreted with caution and may require discussion with a Clinical Virologist.
In the immunocompetent (>12 months age) patient the following assay result combinations serve as an interpretative guideline
| CMV IgG | CMV IgM | Interpretation |
| Negative (<0.5 U/mL) | Negative | No evidence of previous exposure or current infection. Susceptible to primary infection |
| Positive (1.0 U/mL or more than that) | Negative | Evidence of historical exposure. Not currently infected. |
| Negative (<0.5 U/mL) | Positive | Presumptive evidence of possible primary infection. Repeat testing in 1-2 weeks to check for CMV IgG seroconversion |
| Positive (1.0 U/mL or more than that) | Positive | Presumptive evidence of CMV infection. Repeat testing in 1-2 weeks may be useful to check for a possible increase in CMV IgG level (i.e. an evolving immune response) |
Dr. Gary McAuliffe GMcAuliffe@adhb.govt.nz - Clinical Virologist
Dr. Erasmus Smit ErasmusS@adhb.govt.nz - Clinical Virologist
Centrifuge
primary blood specimens and / or separated serum and
transport
with refrigerated chiller packs (4
0
C)