What is CMV IgG avidity test?
What is CMV IgG avidity test?
IgG avidity assays measure the binding strength between IgG antibodies and virus that can help distinguish a primary CMV infection from a past infection. Following primary CMV infection, IgG antibodies have low binding strength (low avidity) then over 2-4 months mature to high binding strength (high avidity).
What is the difference between CMV IgG and IgM?
Testing for CMV infection is a simple blood test, called a CMV IgG antibody. It will determine if a pregnant woman has had CMV. A positive result indicates a current or past CMV infection. A second blood test, called CMV IgM antibody will help determine if the CMV infection is current or past.
What is IgM avidity?
Avidity (functional affinity) is the accumulated strength of multiple affinities. For example, IgM is said to have low affinity but high avidity because it has 10 weak binding sites for antigen as opposed to the 2 stronger binding sites of IgG, IgE and IgD with higher single binding affinities.
What does CMV IgG positive and CMV IgM negative mean?
If there is a 4-fold increase in IgG between the first and second sample, then you have an active CMV infection (primary or reactivated). A positive CMV IgM and negative IgG means you may have very recently been infected.
Is CMV IgG curable?
CMV spreads from person to person through body fluids, such as blood, saliva, urine, semen and breast milk. There is no cure, but there are medications that can help treat the symptoms.
Is high avidity good?
High or intermediate avidity indicates a low risk of congenital infection, whereas low avidity indicates an increased risk. If the result indicates low avidity, the patient should be counseled that vertical transmission is not a foregone conclusion, and additional procedures can be employed to identify fetal infection.
Why is IgG higher affinity than IgM?
Due to the affinity maturation and class switching processes, IgG and IgA antibodies typically have substantially higher affinities than IgM antibodies [18,19]. Consequently, IgG antibodies often outcompete IgM antibodies for antigens, making it difficult to reliably measure IgM levels.
How is CMV IgG positive treated?
- Ganciclovir treatment. The drug of choice for treatment of CMV disease is intravenous ganciclovir, although valganciclovir may be used for nonsevere CMV treatment in selected cases.
- Ganciclovir prophylaxis.
- Letermovir prophylaxis.
- Acyclovir prophylaxis.
- Cidofovir prophylaxis.
What is a normal CMV IgG level?
The IgG for CMV normal range is 620 to 1400 mg/dl. If the reading is above this threshold, then you will need to consult a doctor to prevent any unwanted symptoms or infections.
What does high IgG avidity mean?
(ii) An IgG-positive, IgM-positive result suggests recent primary infection and should trigger CMV IgG avidity testing. High or intermediate avidity indicates a low risk of congenital infection, whereas low avidity indicates an increased risk.
What is the role of CMV IgG avidity testing?
Role of cytomegalovirus (CMV) IgG avidity testing in diagnosing primary CMV infection during pregnancy The risk of intrauterine transmission of cytomegalovirus (CMV) during pregnancy is much greater for women who contract primary CMV infection after conception than for women with evidence of infection (circulating CMV antibodies) before conception.
When do negative CMV IgM results indicate primary infection?
Individuals with negative CMV IgG results are presumed to not have had prior exposure or infection with CMV and are, therefore, considered susceptible to primary infection. Equivocal CMV IgM or IgG results may occur during acute infection or may be due to nonspecific binding reactions.
When to use CMV avidity in PCR screen?
If CMV IgM positive, direct detection of virus by PCR viral load is indicated (see CMV viral load) CMV avidity can be used to indicate how recently infection has occurred. This is usually of use in pregnancy and should only be requested after discussion with a Consultant Microbiologist CMV CFT is part of the following viral screen sets:
When does IgG avidity mature after primary infection?
IgG avidity is defined as the strength with which IgG binds to antigenic epitopes expressed by a given protein; it matures gradually during the 6 months following primary infection.