Cytomegalovirus PCR Quantitative

Cytomegalovirus (CMV) is a member of the Herpesviridae family of viruses and usually causes asymptomatic infection after which it remains latent in patients, primarily within bone marrow derived cells. Primary CMV infection in immunocompetent individuals may manifest as a mononucleosis-type syndrome, similar to primary Epstein-Barr virus infection, with fever, malaise and lymphadenopathy.

CMV is a significant cause of morbidity and mortality among bone marrow or solid organ transplant recipients, individuals with AIDS, and other immunosuppressed patients. They can become ill from a newly acquired primary infection or by virus reactivation. CMV also infect newborns and is classified as one of the TORCH infections (toxoplasmosis, other infections including rubella, CMV, and herpes simplex virus).

Although the virus can be isolated from a variety of sources, viremia correlates best with clinically significant CMV disease. CMV DNA is extracted from plasma. It is then amplified and detected by real time quantitative PCR. Primers detect the Us9 gene of CMV. Detection of CMV DNA in plasma is consistent with an active infection. The quantitative range is 34.5 to 10,000,000 IU/mL (1.54-7.00 log IU/mL). If PCR detects the presence of virus but was not able to accurately quantify the viral load, the result is reported as “Not Quantified, Detected.” 

Quantitative PCR is recommended to monitor transplant recipients for the development of CMV disease.  Monitoring patients weekly after transplant with a quantitative CMV PCR assay can be used to guide preemptive therapy for CMV infection. Monitoring viral load after completion of therapy may be useful in predictive relapsing disease.

Reference value is a negative result.

Specimen requirement is one lavender (EDTA) top tube of blood. PCR can also be performed on urine, CSF, bone marrow, amniotic fluid, respiratory fluids, other body fluids, eye swabs, and fresh frozen tissue. 

References

Binnicker MJ, Espy M. Comparison of six real-time PCR assays for the qualitative detection of cytomegalovirus in clinical specimens. J Clin Microbiol. 2013:51(11):3749-3752.

Nitsche A, et al. Detection of human cytomegalovirus DNA by real-time quantitative PCR. J Clin Microbiol. 2000 Jul;38(7):2734-7.