Parvovirus (B19 IgG)

1. When should this test be requested?

Parvovirus B19 testing is generally unnecessary when a child exhibits the characteristic "slapped cheek" and lacy rashes, as these distinctive rashes are typically sufficient for a healthcare provider to diagnose the infection. For most individuals with or without a history of parvovirus B19, laboratory testing is usually not required, given that the illness typically resolves within 5-7 days and the symptoms are generally mild.

Parvovirus B19 IgG and IgM antibody tests may be ordered when a pregnant woman experiences flu-like symptoms and/or has had exposure to someone with a parvovirus B19 infection. These tests aim to ascertain if she is actively infected, has had a recent infection, or has been previously exposed. In certain cases, DNA testing may be conducted on fetal samples.

Antibody testing and/or DNA testing may be requested when an individual presents with acute or persistent anemia or joint pain, and the healthcare provider suspects a parvovirus B19 infection as the potential cause. Parvovirus B19 DNA testing is typically considered for individuals with compromised immune systems.

In situations where the initial results are negative but a healthcare provider still suspects a parvovirus infection or when monitoring changes in antibody levels over time is necessary, one or more parvovirus B19 tests may be repeated.

2. How this test is used?

Parvovirus B19 testing is typically reserved for cases of active infection and to assess immunity, especially in individuals at an elevated risk of complications, such as those with sickle cell anemia. Various methods are used for detecting a parvovirus B19 infection:

1. Antibody Testing:

- Two types of parvovirus B19 antibodies may be produced in response to an infection: IgM and IgG.

- IgM antibodies are the initial response to a parvovirus infection, typically appearing within one to two weeks after exposure. IgM production increases temporarily and then diminishes. Eventually, IgM antibody levels usually become undetectable.

- IgG antibodies are generated several weeks after the initial infection, providing long-term protection. IgG levels rise during the active infection and then stabilize as the parvovirus B19 infection resolves. Following exposure to parvovirus B19, an individual will retain measurable IgG antibody levels in their blood for the rest of their life.

- Parvovirus B19 antibody testing helps assess immunity in pregnant women exposed to someone with the virus or those exhibiting symptoms suggestive of parvovirus infection. It may also be ordered for individuals with acute or chronic anemia or persistent joint pain linked to a parvovirus B19 infection. By analyzing the presence or absence of both IgG and IgM in the same sample, healthcare providers can distinguish between current, recent, and previous infections. Typically, antibody testing is not conducted on children displaying characteristic fifth disease rashes, and general population screening is infrequent due to the widespread nature of parvovirus B19 infections, which usually pose minimal risks to individuals with healthy immune systems.

1. Viral Detection:

- Viral detection entails the identification of parvovirus B19 genetic material (DNA) in a blood sample, or less commonly, in samples of bone marrow, fetal cord blood, or amniotic fluid.

- Parvovirus B19 DNA testing is primarily performed to detect active parvovirus infections in individuals with compromised immune systems and acute or persistent anemia. These individuals may not generate a sufficient quantity of antibodies to be detected or to resolve the infection.

- This testing may also be conducted to identify the presence of the virus in infants when their mothers are infected or have been exposed during pregnancy.

3. How is the result interpreted?

Antibody Testing:

• If both parvovirus B19 IgG and IgM are detected, it is probable that the individual tested has an active infection or has recently experienced one. This can be confirmed by reevaluating IgG levels within 2 or 3 weeks. The concentration of IgG, rather than the absolute level, is more significant. If there is a fourfold increase in IgG between the initial and subsequent sample, it indicates an active infection or a recent one.
• When only IgM is present, it suggests that the person might have been infected very recently, typically within the past 2 to 4 months. If only parvovirus B19 IgG is detected, it signifies a previous parvovirus infection, providing ongoing protection against the virus.
• Negative antibody test results indicate that the person has not been infected and lacks immunity. In the case of non-immune pregnant women who have been exposed to someone with the disease, close monitoring by a physician is usually recommended.
• In situations where an individual displays symptoms but exhibits low or undetectable levels of IgG and/or IgM, it may indicate a condition other than parvovirus B19 or an immune system that is not responding as expected. This can occur when the immune system fails to produce sufficient antibodies, even if parvovirus is present. This situation is common among individuals with weakened immune systems (immunocompromised), and DNA testing may be necessary.

Viral Detection:

• A positive parvovirus B19 DNA test confirms an ongoing infection with the virus. However, a negative result does not rule out infection, as the viral load in the sample may be insufficient for detection.
• Fetal parvovirus B19 infection is frequently identified through testing maternal samples and samples from the baby.
• Polymerase chain reaction (PCR) is employed to detect viral DNA and is the preferred method for identifying chronic infections in immunocompromised patients, as antibody levels can be inconsistent.

4. Is this the same parvovirus that impacts dogs and cats? Can I contract it from my pet?

No, distinct strains of parvovirus affect both humans and animals. You cannot contract parvovirus from your pets, and likewise, they cannot acquire it from you.

5. How should I prevent getting a parvovirus B19 infection?

A vaccine for parvovirus is not currently accessible. The virus spreads through close contact, and individuals can be contagious even in the absence of symptoms. However, practicing thorough hygiene, including frequent handwashing and covering the mouth and nose when coughing or sneezing, can aid in averting virus transmission. Parvovirus infections are most common during childhood.