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Specimen Collection

A dedicated specimen (i.e. no other tests to be performed) is required for this assay.

For all CMV Viral Load requests on EDTA or PPT samples.

Do NOT use Heparin or Serum tubes.

2 mL Paediatric EDTA Whole Blood (Always Required)
5 mL PPT Plasma (Preferred)

Centrifuge PPT tube within 6 hours of collection.

Transport at 2 - 8 ^o C if transport time from collection is less than 5 days.

Plasma need to be separated and frozen after 5 days. Unseparated specimens are unsuitable for analysis after this time

Do not freeze unseparated PPT tubes. If the specimen requires freezing, the plasma must be removed from the gel first.

4 mL EDTA Plasma

Centrifuge EDTA tube within 24 hours of collection and separate plasma.

Transport at 2 - 8 ^o C if transport time from collection is less than 72 hours. Transport frozen if more than 72 hours.

1 mL Sterile Container Urine
Reference Intervals

Infant <3 weeks of age: presence of CMV in the urine is diagnostic of congenital CMV

Infant >3 weeks of age: presence of CMV in urine could be either postnatally acquired or congenital CMV. Absence of CMV in urine exclude congenital CMV as CMV is excreted in the urine for the first couple of months of life.

Turnaround Time: Within 2 days

Turnaround Time: Within 2 days

Tested weekdays.

Assay Method

As from 10 ^th October 2022, CMV viral load assay will transfer from the Roche COBAS 4800 platform to the Roche COBAS 6800 platform.

Viral load results are expected to be unchanged:

•   Linear range = 34.5 to 1.0E+07 IU/mL

•   Limit of detection (EDTA Plasma) = 34.5 IU/mL

Note: CMV viral load is reported in International Units (IU) and log IU. One IU equates to 1.09 viral copies.

Diagnostic Use and Interpretation

High levels of plasma CMV DNA are closely correlated with clinical disease in immunosupressed patients. Virus quantitation may be used to predict or identify CMV disease. 

To diagnose congenital CMV in first 3 weeks of birth, request urine CMV PCR. Urine PCR can be used to exclude, but dot diagnose congenital CMV after 3 weeks of age. Request Guthrie card for CMV PCR in urine PCR positive cases after 3 weeks of age.

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.

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

 

References.

1.  M. Hiyoshui, et al. Evaluation of the Amplicor CMV test for direct detection of Cytomegalovirus in plasma specimens. J. Clinical Microbiology. 1977; 35, 2692-2694

2.  G. Bovin et al. Quantitative analysis of Cytomegalovirus (CMV) viraemia using the pp65 antigenemia assay and the Cobas Amplicor CMV Monitor PCR test after blood and marrow Allogenic transplantation. J. Clinical Microbiology. 2000; 38, 4356-4360

3.  AM Caliendo et al. Comparison of quantitative Cytomegalovirus (CMV) PCR in plasma and CMV antigenemia assay. Clinical utility of the prototype Amplicor CMV Monitor test in transplant recipients. J. Clinical Microbiology. 2000; 38, 2122-2127

CMV drug resistance

Contact Information

For further information contact the laboratory (contact via Lablink: 22000 or (09) 307-8995 or 0800 522 7587) or email the Virology team virology@adhb.govt.nz

 

Specimen Transport Instructions for Referring Laboratories

See above for preferred 'Specimen Collection and Transport' details. 

A dedicated (i.e.no other tests requested) EDTA/PPT specimen >2mL is always required.

• Whole blood collected in Lavender top tubes or in sterile tubes using EDTA as the anticoagulant may be stored and/or transported for up to 36 hours at 2 to 25 ^o C prior to centrifugation and subsequent testing.

• Alternatively EDTA plasma samples may be stored in primary tubes for up to 36 hours at 2 to 25 ^o C or 6 days at 2 to 8 ^o C following centrifugation.

• Plasma samples may be stored in secondary tubes for up to 36 hours at 2 to 30 ^o C, up to 6 days at 2 to 8 ^o C or up to 6 weeks at -15 to -25 ^o C

• Plasma samples in secondary tubes are stable for up to 3 freeze/thaw cycles when stored frozen at -15 to -25 ^o C

Last updated at 15:46:58 01/12/2022