Home Biomarkers CMV AB IgG

CMV AB IgG

Hepatitis Biomarker

Sample Needed

Collection Type: Blood

Body System

Related System: Hepatitis

Overview

Cytomegalovirus (CMV) IgG is an antibody produced by the immune system after exposure to CMV, a common herpesvirus. The CMV IgG test measures the presence and amount of these long-lived antibodies to determine past infection or immune status. It is used when CMV infection or prior exposure is suspected—particularly in pregnant women, newborns, transplant candidates, and immunocompromised patients—because primary CMV infection, reactivation, or congenital transmission can cause hepatitis, febrile illness, organ dysfunction, or developmental problems. Symptoms prompting testing include fever, jaundice, abnormal liver tests, lymphadenopathy, or pregnancy-related concerns. Results vary by age (higher seroprevalence with increasing age and in certain populations), pregnancy status (maternal IgG crosses placenta), and immune status (immunosuppressed patients may reactivate latent infection).

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Test Preparation

No special preparation is required

Why Do I Need This Test

Profile: Included in some extended viral/hepatitis or infectious-disease panels and prenatal screening.
Symptoms indicating testing: unexplained fever, elevated liver enzymes, jaundice, lymphadenopathy, or maternal concern during pregnancy.
Conditions diagnosed/monitored: past CMV exposure (serostatus), assessment of congenital infection risk, monitoring transplant or immunocompromised patients for reactivation.
Reasons for abnormal levels: recent primary infection, past exposure with established immunity, reactivation in immunosuppression, or passive maternal antibody in neonates.
Biological meaning: Positive IgG generally indicates past infection or immunity; rising titers or concurrent IgM suggests recent/active infection.
Behaviors/lifestyle: close contact with young children or exposures in healthcare/childcare increase risk of acquiring CMV.
Family history: prior congenital CMV in a sibling or household members with CMV may prompt testing in pregnancy or newborns.

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Understanding Test Results

Negative (<0.9 index or <6.0 AU/mL): No detectable CMV IgG suggests no prior exposure; in pregnancy this indicates susceptibility to primary infection and baseline testing is recommended for follow-up if exposure occurs.
Equivocal (0.9–1.1 index or 6.0–10 AU/mL depending on assay): Indeterminate repeat testing in 1–3 weeks or perform IgM and/or PCR to clarify recent infection.
Positive (>1.1 index or >10 AU/mL): Prior CMV infection and likely immunity.
By itself, isolated IgG positivity usually reflects past infection; it does not prove active disease.
If IgG is positive with concurrent IgM or a rising IgG titer on paired samples, this indicates recent/acute infection and higher risk for complications (including congenital infection if in pregnancy).
In immunocompromised patients, positive IgG indicates latent infection with potential for reactivation; monitoring with PCR and clinical assessment is warranted.
False positives can occur from cross-reactivity; interpret with clinical picture and additional tests (IgM, avidity testing, PCR) when needed.

Normal Range

Negative: <0.9 index OR Negative: <6.0 AU/mL

FAQs

Q: What does CMV IgG AB positive mean?

A: A positive CMV IgG antibody test means you were exposed to cytomegalovirus in the past and have IgG antibodies. It generally indicates prior infection and some immunity, not an active or recent infection (those are suggested by IgM or low IgG avidity). In pregnancy or if symptomatic, further testing and clinical evaluation are recommended.

Q: Does CMV IgG positive need treatment?

A: CMV IgG positivity usually indicates past exposure and typically does not require treatment in healthy people. Therapy is only considered if there’s evidence of active or recent infection (positive IgM or PCR), symptoms, pregnancy with suspected primary infection, congenital infection in a newborn, or immunocompromise; these situations need specialist evaluation and possible antiviral treatment or further testing.

Q: How long is CMV IgG positive?

A: CMV IgG antibodies typically develop within weeks after infection and remain positive for life, indicating past exposure or immunity. IgG levels may fluctuate but generally persist; true loss of IgG is uncommon except with severe immunodeficiency or rare seroreversion. To assess timing, clinicians use IgM, rising IgG and IgG avidity testing to distinguish recent versus remote infection.

Q: What is a CMV test used for?

A: A CMV test detects cytomegalovirus infection and distinguishes current (IgM, PCR) from past exposure (IgG). It’s used to screen pregnant women and diagnose congenital infection in newborns (saliva/urine PCR), monitor viral load in immunocompromised or transplant patients, and guide treatment decisions. Testing also assesses immunity to inform preventive measures during pregnancy or before transplantation.

Q: Is it good to be CMV positive?

A: Being CMV‑IgG positive means past cytomegalovirus infection and lifelong latent virus. For most healthy adults this is harmless and may reduce risk of a new primary infection. It isn’t inherently “good,” since reactivation or reinfection can harm immunocompromised people and congenital infection risk matters in pregnancy. If pregnant or immunosuppressed, discuss testing and management with your healthcare provider.

Q: How do people get CMV?

A: CMV spreads when a person is exposed to body fluids—saliva, urine, blood, tears, semen, and cervical/vaginal secretions— through close contact, kissing, sexual activity, or sharing utensils. It can cross the placenta causing congenital infection, and be transmitted via breastfeeding, blood transfusion, or organ transplant. Infected people often shed virus without symptoms, and immunocompromised individuals face higher risk.