Cytomegalovirus (CMV) PCR (Quantitative) - blood specimen
- LIS Mnemonic: CMVPCRQT
Collect
Lavendar (EDTA)
Volume Required
4-7 ml whole blood; for infants a volume of 2-4 ml is acceptable
Minimum Required
4 ml whole blood; for infants a volume of 2 ml is acceptable
Transport
Transport blood in a timely fashion (preferably within 8 hours of collection) at room temperature to the Clinical Virology Laboratory.
Stability
N/A
Processing
Whole blood in an EDTA-anticoagulated tube is the preferred specimen source. Thoroughly mix the blood by gently inverting the collection tube 6-12 times before sending to the laboratory. Other acceptable specimens include body fluids, tissue submitted in viral transport medium, and CSF.
Unacceptable conditions
Clotted specimens
Days Performed
Daily
Reported
Same day
Reflex Testing
When monitoring the blood of immunocompromised patients for CMV over time, a quantitative PCR assay will be automatically performed on all patients whose blood has been previously positive for CMV by qualitative and/or quantitative PCR testing.
CPT
87497
Methodology
Amplification and detection of CMV DNA polymerase gene using TaqMan real-time PCR technology. This test is performed pursuant to an agreement with Roche Molecular Systems, Inc.
Disease Information
Utility:
CMV infections are common and usually asymptomatic in otherwise healthy children and adults; however, the incidence and spectrum of disease in newborns and in immunocompromised hosts establish this virus as an important human pathogen. Real-time PCR is widely used for the direct detection and quantification of CMV from blood leukocytes in recipients of solid-organ and bone marrow transplants, cancer patients (particularly those with leukemia and lymphoma receiving chemotherapy), and individuals infected with HIV who are suspected of having systemic CMV infection. Quantitative measures of CMV DNA can provide a rapid diagnosis of established disease, identify patients at risk of developing disease, assess the progression of disease and the risk of relapse, direct the initiation of preemptive therapy, monitor the response to antiviral therapy, and predict treatment failure and the emergence of drug-resistant virus. In general, patients with active CMV disease are viremic and have elevated levels of CMV DNA in their blood; a rapid rise in CMV DNA copy number correlates with the progession to or presence of symptoms and drug failure during treatment.
Interpretation
If positive, quantity of cytomegalovirus DNA is reported in copies/ml and log10 values. Dynamic range of the assay is 500 copies/ml to 3.74 million copies/ml or 2.70 log10 copies/ml to 6.57 log10 copies/ml.
Reference Values
Negative or quantity of cytomegalovirus DNA is less than the lower limit of detection
Remarks
Quantitative viral load results are best reflected when reported using log transformed units of copies/ml of nucleic acid. Logarithmic expression best reflects the process of viral replication and is less subject to over-interpretation of minor (non-clinically significant) changes. For this reason, all viral load results are reported not only as copies/ml but log10 copies/ml of nucleic acid.
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