Cytomegalovirus Ab, IgG

Laboratory assay overview

This test is used to aid in the determination of CMV serological status. CMV-specific IgG class antibodies rise gradually following infection and persist life-long. This assay can be used to identify individuals previously infected with CMV and at risk for reactivation as well as donors with the potential to transmit virus. This assay cannot be used to determine the timing of infection.

Laboratory assay overview

This test is used to aid in the determination of serological status to CMV and establish the recency of infection when CMV IgG is present.

Laboratory assay overview

This test is intended to aid in the diagnosis of current or recent cytomegalovirus (CMV) infection. Isolated CMV IgM- positive results should not be used to diagnose primary CMV infection, as IgM may persist for more than 12 months after infection or occur during secondary infection or viral reactivation. Primary infection is best demonstrated by CMV IgG seroconversion in paired specimens. When CMV IgG is detectable, CMV IgG avidity testing may aid in assessing the recency of infection. Active CMV infection may be confirmed by nucleic acid amplification testing (NAAT). In the United States, nearly one in three children is already infected with CMV by age 5, and more than half of adults have been infected by age 40. Primary CMV infection in immunocompetent individuals typically follows an asymptomatic or subclinical course. Mononucleosis is the most prevalent presentation of CMV in patients with an intact immune system, characterized by fever, rash and lymphocytosis. Immunocompromised individuals, infants infected in utero, and low birth weight and premature infants are at higher risk for serious complications from CMV infection, both primary and reactivation. Infection in these groups can impact multiple organ systems and is associated with increased morbidity. CMV is the most common congenital infection, and the risk of CMV complications (e.g., birth defects including hearing loss) in the fetus is greatest if a primary infection occurs during the first trimester. In infants, children and adults, viremia can be detected for two to three weeks after a primary infection, and IgM becomes detectable at about 28 to 60 days followed by a detectable IgG antibody response. Nucleic acid amplification testing is recommended for the diagnosis of congenital CMV in newborns (up to 12-18 months) and for monitoring infection is transplant recipients. In individuals older than 12 months, including pregnant individuals, a positive CMV IgG test indicates infection with CMV at some time during their life but does not indicate when they were infected. Measurement of CMV IgG in paired samples taken some one to three months apart can be used to diagnose primary infection. Seroconversion (acute serum IgG negative, convalescent serum IgG positive) is evidence of primary infection. The clinical utility of CMV IgM is more limited as the detection of CMV IgM in itself cannot be used to diagnose primary CMV infection because IgM can also be present during secondary CMV infection and reactivation. IgM positive results in combination with low IgG avidity results are considered reliable evidence for primary infection. For more detailed differentiation of primary and past infections, IgG avidity assays are useful. IgG avidity assays measure the binding strength between IgG antibodies and virus and can help distinguish a primary CMV infection from a past infection. Following primary CMV infection, IgG antibodies have low binding strength (low avidity), then within two to four months they mature to high binding strength (high avidity). While commercial assays for avidity testing are available, they need further standardization and should be interpreted with caution.

Laboratory assay overview

Intrauterine or congenital CMV infections occur in 0.5 to 2.2% of all live births. Symptomatic congenital infections usually occur in infants born to non-immune mothers who have primary infections during pregnancy. Latency and reactivation of CMV influence the interpretation of serological results. A single positive CMV IgG result is and indication of present or past infection. The presence of CMV IgM suggests a recent CMV exposure but does not differentiate between primary infection and reactivation.

Quest Diagnostics population reference ranges

Quest Diagnostics calculates these statistical intervals for this specific assay and demographic group, not as universal optimal targets.

Laboratory assay overview

CMV infections are common and usually asymptomatic. In patients who are immunocompromised, CMV may cause severe disseminated disease. CMV may cause birth defects in a minority of infected newborns. CMV IgG antibodies may represent prior exposure or recent infection.

Quest Diagnostics population reference ranges

Quest Diagnostics calculates these statistical intervals for this specific assay and demographic group, not as universal optimal targets.

Laboratory assay overview

CMV: Routine screening of pregnant people for CMV is not recommended by current guidelines. Maternal CMV IgM antibody has limited clinical utility in differentiating primary from recurrent infection. An IgG-positive, IgM-negative result typically indicates past infection; however, IgG avidity testing, to determine the time since primary infection, should be considered if clinically warranted. An IgG-positive, IgM-positive result suggests recent primary infection and IgG avidity testing is recommended to determine the time since primary infection. An IgG-negative, IgM-positive result suggests very recent infection and the patient should be followed to document seroconversion. An IgG-negative, IgM-negative result indicates susceptibility to infection. Parvovirus B19: Routine screening of pregnant people for parvovirus B19 is not recommended by current guidelines. Testing should be performed for those patients with symptoms consistent with parvovirus B19 infection or for those with exposure to suspected or confirmed acute infections. Women who are negative for both IgG and IgM are susceptible to parvovirus B19 infection, and serologic testing should be repeated in four weeks. Toxoplasma: Routine screening of pregnant people for toxoplasmosis is not recommended by current guidelines and should be limited to immunosuppressed or HIV-positive individuals. An IgG-positive, IgM-negative result typically indicates past infection. Toxoplasma IgM may persist for many months or years after acute infection, and false-positive test results are common. IgG-negative, IgM-positive results suggest possible very recent infection and should be followed to document seroconversion. An IgG-positive, IgM-positive result suggests recent primary infection, and IgG avidity testing is recommended to determine the time since primary infection.

Laboratory assay overview

This test is used to detect TORCH antibodies and aid in the diagnosis of congenital infection.

Laboratory assay overview

This panel may provide antibody-based evidence of a recent or previous infection with Toxoplasma gondii, rubella virus, cytomegalovirus, and/or herpes simplex virus in pregnant individuals. This panel is generally ordered as part of a prenatal evaluation of a patient who is at risk of infection with these microbial agents. However, routine serology testing for these infections as a group has low diagnostic yield for non-specific ultrasound abnormalities of fetuses [1,2]. Some maternal infections during pregnancy may be associated with miscarriage, stillbirth, or fetal abnormalities. These infections may be primary (ie, occur for the first time) or the result of reactivation of prior infections (eg, herpes simplex virus or cytomegalovirus). Infections with these pathogens may have a subclinical course in the mother and transmit to the infant during the prenatal or perinatal period [3]. Testing for infections in pregnant persons should be guided by pathogen-specific clinical features, risk factors, and prevalence [1]. The American Academy of Pediatrics Committee on Fetus and Newborn and American College of Obstetricians and Gynecologists Committee on Obstetric Practice recommend serologic screening for evidence of rubella immunity at the first prenatal visit [3]. Routine serologic screening of pregnant individuals for Toxoplasma and cytomegalovirus is not recommended [3]. Type-specific serologic testing for herpes simplex virus may be useful in the evaluation of risk for infection or confirmation of suspected infection [3,4]. This panel is not recommended for use in documenting newborn congenital infections. In this clinical situation, consider requesting the Torch Panel, Acute. The results of this test panel should be interpreted in the context of pertinent clinical findings. References 1. Fitzpatrick D, et al. Prenat Diagn. 2022;42(1):87-96. 2. Society for Maternal-Fetal Medicine (SMFM), et al. Am J Obstet Gynecol. 2020;223(4):B2-B17. 3. American Academy of Pediatrics Committee on Fetus and Newborn and American College of Obstetricians and Gynecologists Committee on Obstetric Practice. Guidelines for Perinatal Care. 8th ed. 2017. Accessed April 28, 2022. 4. Workowski KA, et al. MMWR Recomm Rep. 2021;70(4):1-187.