Cytomegalovirus - CMV

Diagnosis

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
  • Neonatal 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)

Histology

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

Prognosis

  • 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

Clinical Background

Cytomegalovirus (CMV) is generally asymptomatic in immunocompetent children and adults, but is a potentially significant disease in immunocompromised hosts, neonates, and pregnant females.

Epidemiology

  • 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

Organism

  • 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

  • CMV diseases and related syndromes

    CMV Diseases and Related Syndromes

    CMV disease

    Principal syndrome

    Risk factors

    Primary infection in immunocompetent individualOften asymptomatic, fever, myalgies, flu-like syndrome, mononucleosis-like syndrome, hepatitis 
    AIDS/HIV

    Pulmonary disease – pneumonia

    Ophthalmic disease – retinitis

    GI disease – gastritis, colitis, esophagitis

    CNS disease – encephalopathy, neuropathy

    CD4+ cells <100/mL

    Previous CMV infection

    CongenitalCytomegalic inclusion disease – hepatosplenomegaly, microcephaly,  developmental delay, sensorineural hearing loss, seizures, hypotenia, blueberry muffin syndrome, intrauterine growth restrictionEarly maternal primary infection or reinfection (first trimester)
    Organ transplantation

    Pulmonary disease – pneumonia

    GI disease – esophagitis, gastritis, colitis, hepatitis

    Disseminated disease

    Tissue invasive disease – nephritis, myocarditis, cystitis, pancreatitis

    Seronegative recipient with seropositive donor (risk increased most with intensive suppression)

    Immunosuppression

    Bone marrow transplant

    Enhanced graft vs host disease; rejection

    Pulmonary disease – pneumonitis

    GI disease – gastritis, colitis, hepatitis

    Disseminated disease

    Older age

    Seropositive recipient

    Seropositive donor

Prevention

  • 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

Indications for Laboratory Testing

  • 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
Test Name and Number Recommended Use Limitations Follow Up
Cytomegalovirus Rapid Culture 0065004
Method: Cell Culture/Immunofluorescence

Aids in diagnosis of active cytomegalovirus infection; molecular testing is generally preferred

Recommended for detecting CMV in specimens other than CSF; gold standard test for tissue

High sensitivity and specificity

   
Cytomegalovirus by Qualitative PCR 0060040
Method: Qualitative Polymerase Chain Reaction

Detects cytomegalovirus but does not quantify viral load; potentially useful for specimen types other than blood

Standard of care for diagnosing CMV in CSF

Relatively rapid test to diagnose CMV in immunocompromised patients or solid organ donors (not tissue donors)

May be performed on amniotic fluid

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

 
Cytomegalovirus by PCR, Whole Blood or Bone Marrow 0060031
Method: Qualitative Polymerase Chain Reaction

Detects cytomegalovirus in whole blood or bone marrow but does not quantify viral load; quantitative cytomegalovirus PCR testing on patient plasma is preferred for most clinical indications

Relatively rapid test to diagnose CMV infection

   
Cytomegalovirus by Quantitative PCR 0051813
Method: Quantitative Polymerase Chain Reaction

Determine acute CMV infection

Use for suspicion of cytomegalovirus (CMV) infection during pregnancy as indicated by positive IgM and/or IgG tests

Monitoring in organ transplant (solid and hematopoietic stem cell), HIV patients, and other immunocompromised settings

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

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

Diagnose CMV infection

Monitor disease state in solid organ transplant and HIV patients

Reflex pattern – if CMV quantitative PCR result is ≥3.2 log (1600 copies/mL), then CMV antiviral drug resistance by sequencing will be added

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

Aid in the determination of recent (previous 3-4  months) or past (>3 months) CMV infection, particularly in pregnant females

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

Aids in discriminating between current and past cytomegalovirus infection in immunocompetent individuals

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

Aid in histologic diagnosis of CMV

Stained and returned to client pathologist for interpretation; consultation available if needed

   
Additional Tests Available
 
Click the plus sign to expand the table of additional tests.
Test Name and NumberComments
Cytomegalovirus Antibody, IgM 0050553
Method: Semi-Quantitative Chemiluminescent Immunoassay

Use for suspicion of cytomegalovirus (CMV) infection during pregnancy as indicated by positive IgM and/or IgG tests

CMV serology is not useful for the evaluation of active or reactivated infection in immunocompromised patients; molecular diagnostic tests (ie, PCR) are preferred in these cases

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

Cytomegalovirus Antibody, IgG 0050165
Method: Semi-Quantitative Chemiluminescent Immunoassay

Determine previous CMV infection

Use for suspicion of cytomegalovirus (CMV) infection during pregnancy as indicated by positive IgM and/or IgG tests

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

Cytomegalovirus Antiviral Drug Resistance by Sequencing 2004760
Method: Polymerase Chain Reaction/Sequencing
TORCH Antibodies, IgG 0050772
Method: Semi-Quantitative Chemiluminescent Immunoassay/Quantitative Chemiluminescent Immunoassay
TORCH Antibodies, IgM 0050665
Method: Semi-Quantitative Chemiluminescent Immunoassay/Semi-Quantitative Enzyme-Linked Immunosorbent Assay
Viral Culture, Non-Respiratory and Cytomegalovirus Rapid Culture 2006496
Method: Cell Culture/Immunofluorescence

For best results, specify specimen source and suspected virus on order form; molecular diagnostics are preferred for suspected invasive CMV

Viruses that can be isolated – adenovirus, CMV, enterovirus, HSV, and VZV

Virus-specific tests are recommended

Viral Culture, Non-Respiratory 2006498
Method: Cell Culture

Generally, virus-specific testing (eg, antigen detection or molecular) is recommended

Viruses that can be isolated by culture – adenovirus, CMV, enterovirus, HSV, and VZV

Virus-specific tests are recommended

Viral Culture, Respiratory 2006499
Method: Cell Culture

Detects common respiratory viruses; molecular methods may offer improved sensitivity

Respiratory viruses rapid culture offers faster turnaround time

Viruses that can be isolated – adenovirus; CMV; enterovirus; HSV; influenza A and B; parainfluenza types 1,2, and 3; RSV; and VZV

Virus-specific tests are recommended

Viral Culture, Respiratory and Cytomegalovirus Rapid Culture 2006497
Method: Cell Culture/Immunofluorescence

Molecular diagnostics are preferred for suspected invasive CMV

Viruses that can be isolated – adenovirus; CMV; enterovirus; HSV; influenza A and B; parainfluenza types 1,2, and 3; RSV; and VZV

Virus-specific tests are recommended