Cytomegalovirus - CMV

Cytomegalovirus (CMV) is generally asymptomatic in immunocompetent children and adults, but is a potentially significant disease in immunocompromised hosts, neonates, and pregnant females. The approach to laboratory testing depends upon whether the patient is immunocompetent or immunocompromised. Serology is used in immunocompetent persons, but is not helpful in immunocompromised patients. For these patients, PCR and culture (gold standard) are more helpful.

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Mononucleosis-like illness in immunocompetent patients who test negative for EBV
  • Suspected CMV infection in immunocompromised patients
  • Congenital syndromes suspicious for CMV
  • Pretransplant and posttransplant screening

Laboratory Testing

  • Acute disease confirmation in immunocompetent patients – order acute and convalescent serology
    • Elevated IgM provides evidence of current infection or reactivation
      • Four-fold increase in IgG titers using paired specimens 10-14 days apart is suggestive of recent infection
  •  Acute disease in immunocompromised patients – serology not helpful
    • Quantitative measurement by PCR defines viral load
    • Gold standard – tissue culture
      • Biopsy of affected tissue site or bronchoalveolar lavage
  • Transplant patients
    • Pretransplant screening
      • IgG testing of donor and recipient
      • CMV-specific CD8 T cells – aids in determining risk of CMV infection posttransplant
    • Posttansplant screening
      • Hematopoietic stem cell (HSCT) (Tomblyn, 2009)
        • Screen 7-10 days posttransplant
        • Screen until at least 100 days posttransplant
      • Renal transplant (KIDGO, 2009)
        • Viral load monitoring for patients deemed moderate risk for CMV
  • Primary infection in pregnant women
    • CMV IgG avidity testing to distinguish between primary and secondary infection
      • Low avidity suggests CMV infection within last 3-4 months (increased risk for infant with congenital CMV)
    • Acute and convalescent serology – may be less helpful than avidity testing
      • IgM may remain positive for months
      • IgM may elevate in reactivated disease
      • Use same criteria as immunocompromised patients for active infection
    • Amniotic fluid – PCR testing
      • Most sensitive >21 weeks gestation
  • Congenital disease
    • Rapid culture of urine (early antigen detection)
    • PCR on blood or body fluids
    • Test within first 3 weeks to exclude perinatal infection
    • Consider testing for other congenital syndromes if CMV not clearly identified as etiology of congenital disease
  • Interpretation of CMV laboratory tests (CDC)


  • Presence of characteristic intranuclear and intracytoplasmic inclusions confirms diagnosis
  • Cytomegalovirus IHC stain may be useful in tissue


  • Neonatal – poor outcome associated with the following
    • Cerebrospinal fluid protein >120 mg/dL
    • CT – calcifications/microcephaly
    • Fetal ultrasound – placentomegaly; observed fetal anatomic abnormalities

Differential Diagnosis


  • Incidence
    • ~70% of adults in the U.S. are seropositive
    • 1-2% of U.S. population infected yearly
  • Transmission
    • Transplacental (congenital), perinatal (human milk, cervical secretions)
    • Blood transfusion
    • Organ transplantation (both solid and hematopoietic)
    • Infectious droplet (normal childhood route)
      • CMV excreted in all secretions except tears
    • Sexual contact


  • Largest member of the herpesvirus family; double-stranded DNA virus
  • Ability to remain latent (feature of all herpes viruses)
  • Large intranuclear and cytoplasmic inclusions produced in tissues by CMV are the hallmark of the disease

Risk Factors for Disease

  • HIV
  • Organ transplantation
  • Immunocompromised status
  • Maternal infections or reinfections – leads to congenital disease

Clinical Presentation


  • Blood transfusions
    • Seronegative individuals transfused with blood from seropositive donors have a high risk of developing CMV infection
    • Serologic testing for CMV is important in screening blood for transfusion to neonates or to immunocompromised patients
    • Use of leukocyte-reduced blood products greatly reduces the risk of transfusion-associated transmission
Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Cytomegalovirus Rapid Culture 0065004
Method: Cell Culture/Immunofluorescence

Cytomegalovirus by Qualitative PCR 0060040
Method: Qualitative Polymerase Chain Reaction


PCR on amniotic fluid should be performed >21 weeks' gestation to reduce risk of false negatives

Cytomegalovirus by Quantitative PCR 0051813
Method: Quantitative Polymerase Chain Reaction


The quantitative range of this test is 2.6-6.6 log copies/mL (390-3,900,000 copies/mL) or 2/4-6.4 log IU/mL (227-2,270,000 IU/mL)

One IU/mL of CMV DNA is ~1.72 copies/mL

Negative result (<2.6 log copies/mL [<390 copies/mL] OR <2.4 log IU/mL [<227 IU/mL]) does not rule out presence of PCR inhibitors or DNA concentrations below the level of detection

Inhibition may also lead to underestimation of viral quantitation

Cytomegalovirus, Quantitative PCR with Reflex to Drug Resistance Testing by Sequencing 2006966
Method: Quantitative Polymerase Chain Reaction/Sequencing


Limit of quantification for this DNA assay is 2.6 log copies/mL (390 copies/mL); if the assay DID NOT DETECT the virus, the test result will be reported as <2.6 log copies/mL (<390 copies/mL)

If assay DETECTED presence of virus but was unable to accurately quantify number of copies, test result will be reported as not quantified

Negative result does not rule out presence of PCR inhibitors or DNA concentrations below the level of detection

Cytomegalovirus Antibody, IgG Avidity 2011813
Method: Semi-Quantitative Enzyme-Linked Immunosorbent Assay


Avidity index cannot be calculated for patients who are negative for CMV IgG antibodies

Cytomegalovirus Antibodies, IgG and IgM 0050622
Method: Semi-Quantitative Chemiluminescent Immunoassay


Not recommended for immunocompromised patients

Rise in CMV antibody level may occur in patients with measles, VZV or HSV due to antigenic cross-reactivity within the herpesvirus family

Infants may test positive during first 6 months due to maternal antibodies

Cytomegalovirus (CMV) by Immunohistochemistry 2003833
Method: Immunohistochemistry


Kidney Disease: Improving Global Outcomes (KDIGO) Transplant Work Group. KDIGO clinical practice guideline for the care of kidney transplant recipients. Am J Transplant. 2009; 9 Suppl 3: S1-155. PubMed

Tomblyn M, Chiller T, Einsele H, Gress R, Sepkowitz K, Storek J, Wingard JR, Young JH, Boeckh MJ, Boeckh MA, Center for International Blood and Marrow Research, National Marrow Donor program, European Blood and MarrowTransplant Group, American Society of Blood and Marrow Transplantation, Canadian Blood and Marrow Transplant Group, Infectious Diseases Society of America, Society for Healthcare Epidemiology of America, Association of Medical Microbiology and Infectious Disease Canada, Centers for Disease Control and Prevention. Guidelines for preventing infectious complications among hematopoietic cell transplantation recipients: a global perspective. Biol Blood Marrow Transplant. 2009; 15(10): 1143-238. PubMed

General References

Bhatia P, Narang A, Minz RW. Neonatal cytomegalovirus infection: diagnostic modalities available for early disease detection. Indian J Pediatr. 2010; 77(1): 77-9. PubMed

Boeckh M, Geballe AP. Cytomegalovirus: pathogen, paradigm, and puzzle. J Clin Invest. 2011; 121(5): 1673-80. PubMed

Crough T, Khanna R. Immunobiology of human cytomegalovirus: from bench to bedside. Clin Microbiol Rev. 2009; 22(1): 76-98, Table of Contents. PubMed

de Jong EP, Vossen AC, Walther FJ, Lopriore E. How to use... neonatal TORCH testing. Arch Dis Child Educ Pract Ed. 2013; 98(3): 93-8. PubMed

Del Pizzo J. Focus on diagnosis: congenital infections (TORCH). Pediatr Rev. 2011; 32(12): 537-42. PubMed

DeVries J. The ABCs of CMV. Adv Neonatal Care. 2007; 7(5): 248-55; quiz 256-7. PubMed

Hirsch M, et al. Cytomegalovirus and Human Herpesvirus Types 6, 7, and 8. In Kasper D et al, eds. Harrison's Principles of Internal Medicine, 16th ed. New York: McGraw-Hill, 2005.

Lazzarotto T, Guerra B, Lanari M, Gabrielli L, Landini MP. New advances in the diagnosis of congenital cytomegalovirus infection. J Clin Virol. 2008; 41(3): 192-7. PubMed

Neu N, Duchon J, Zachariah P. TORCH infections. Clin Perinatol. 2015 Mar;42(1):77-103, viii. PubMed

Plosa EJ, Esbenshade JC, Fuller P, Weitkamp J. Cytomegalovirus infection. Pediatr Rev. 2012; 33(4): 156-63; quiz 163. PubMed

Yinon Y, Farine D, Yudin MH. Screening, diagnosis, and management of cytomegalovirus infection in pregnancy. Obstet Gynecol Surv. 2010; 65(11): 736-43. PubMed

References from the ARUP Institute for Clinical and Experimental Pathology®

Hanson KE, Swaminathan S. Cytomegalovirus antiviral drug resistance: future prospects for prevention, detection and management Future Microbiol. 2015; 10(10): 1545-8. PubMed

Kim JH, Goulston C, Sanders S, Lampas M, Zangari M, Tricot G, Hanson KE. Cytomegalovirus reactivation following autologous peripheral blood stem cell transplantation for multiple myeloma in the era of novel chemotherapeutics and tandem transplantation. Biol Blood Marrow Transplant. 2012; 18(11): 1753-8. PubMed

Owen WE, Martins TB, Litwin CM, Roberts WL. Performance characteristics of six IMMULITE 2000 TORCH assays. Am J Clin Pathol. 2006; 126(6): 900-5. PubMed

Prince HE, Lapé-Nixon M, Brenner A, Pitstick N, Couturier MR. Potential impact of different cytomegalovirus (CMV) IgM assays on an algorithm requiring IgM reactivity as a criterion for measuring CMV IgG avidity. Clin Vaccine Immunol. 2014; 21(6): 813-6. PubMed

Ravkov EV, Pavlov IY, Hanson KE, Delgado JC. Validation of cytomegalovirus immune competence assays for the characterization of CD8(+) T cell responses posttransplant. Clin Dev Immunol. 2012; 2012: 451059. PubMed

Medical Reviewers

Last Update: October 2017