IgG to the Epstein–Barr Virus Early Antigen (EA) helps evaluate whether the virus may have been active or reactivated at some point. Early Antigen is a protein produced during the early phase of EBV replication. While most people only develop long-term antibodies to EBV’s Viral Capsid Antigen (VCA) and EBNA proteins, some individuals also develop EA IgG.

EA IgG is sometimes used in conjunction with other EBV markers (VCA IgM, VCA IgG, EBNA IgG) to help understand patterns of:

• Past EBV infection

• Possible reactivation

• Chronic or recurrent EBV activity

However, EA IgG alone does not diagnose acute EBV and often requires correlation with multiple markers.

What It Means When Your EA IgG Result Is Within the Reference Range (Negative)

A negative or normal IgG Early Antigen result means there is no evidence of immune activity directed at EBV’s Early Antigen. In practical terms, this indicates:

• No sign of recent EBV reactivation

• No indication of active viral replication

• No detectable EA-specific immune memory

Because EA IgG is not always produced during routine EBV infections, many healthy individuals remain EA IgG negative even if they had mononucleosis or another EBV infection years earlier. A negative EA IgG result is therefore common and expected.

When EA IgG is within the reference range:

• EBV is not actively replicating

• There is no laboratory support for ongoing or chronic EBV activity

• Past EBV exposure (if present) is considered stable and inactive

This finding is especially meaningful when paired with negative EBV VCA IgM and negative or stable EBV IgG markers.

IgG EB Nuclear Antigen (EBNA IgG) measures long-term antibodies produced after infection with Epstein–Barr virus (EBV). EBNA IgG is a key marker because it typically appears later in the infection, often several months after the initial illness, and then remains detectable for life.

For this reason, EBNA IgG is considered one of the most reliable indicators of past EBV infection. When positive, it helps confirm that someone has previously had EBV and has developed lasting immune memory to the virus.

Clinicians often use EBNA IgG together with VCA IgG, VCA IgM, and Early Antigen (EA) to understand whether an infection is recent, past, or possibly reactivated.

What It Means When Your EBNA IgG Result Is Within the Reference Range (Negative)

A negative or normal EBNA IgG result means there is no detectable antibody response to the EBV Nuclear Antigen. This typically indicates:

• No evidence of a past EBV infection, or

• The infection was very recent, and EBNA antibodies have not yet appeared (less common), or

• Antibody levels are below the detection threshold of the test.

Because EBNA IgG usually becomes positive months after infection and remains elevated for life, most adults who have ever had EBV will test positive. A negative result is therefore most common in:

• Young children

• Individuals who have never been exposed to EBV

• People being tested early in the course of a suspected new infection

When EBNA IgG is within the reference range, and other EBV markers (VCA IgG, EA IgG, VCA IgM) are also negative, this strongly suggests no prior EBV infection.

The IgG Ehrlichia test measures antibodies against Ehrlichia species, bacteria transmitted by ticks that cause ehrlichiosis, a potentially serious tick-borne illness. The two main human pathogens are Ehrlichia chaffeensis (human monocytic ehrlichiosis, HME) and Ehrlichia ewingii. Infections can lead to fever, chills, muscle aches, headache, and sometimes severe complications if untreated.

IgG Epstein–Barr Virus Viral Capsid Antigen (EBV VCA IgG) measures long-term antibodies produced after infection with Epstein–Barr virus (EBV)—one of the most common human viruses. EBV typically causes infectious mononucleosis (“mono”) but can also produce very mild or even unnoticed infections, especially in children.

VCA IgG antibodies usually appear a few weeks after infection and remain detectable for life. Because of this, EBV VCA IgG is a reliable marker for determining whether someone has been infected with EBV at any point in the past.

This marker is most informative when combined with:

• EBV VCA IgM

• EBV Early Antigen (EA)

• EBV EBNA IgG
  Together, these help distinguish past infection, recent infection, and possible viral reactivation.

What It Means When Your IgG EBV VCA Result Is Within the Reference Range (Negative)

A negative or normal EBV VCA IgG result means there is no detectable evidence of a past EBV infection. Your immune system is not showing long-term antibodies to EBV’s Viral Capsid Antigen.

When EBV VCA IgG falls within the reference range:

• You have not been previously infected with EBV, or

• Your antibody level is below the test’s detection limit, which is uncommon but possible in early infection.

• There is no indication of prior mononucleosis, nor of past EBV exposure.

• EBV is not currently active based on this antibody alone.

Most adolescents and adults test positive for EBV IgG because past exposure is extremely common. A negative result simply means you have not developed lasting EBV antibodies yet.

The IgG Immunodominant Peptide C6 (P. C6) test detects antibodies against a highly conserved region of the VlsE protein from Borrelia burgdorferi, the main bacterium that causes Lyme disease. The C6 peptide is considered an immunodominant epitope—a portion of the protein that triggers a strong and reliable immune response across different strains of Borrelia.

The IgG LFA Antigen + CK10 test evaluates long-term antibody responses to both Borrelia antigens (using a lateral flow assay, or LFA) and Cytokeratin 10 (CK10), a structural protein found in epithelial tissues such as the skin. This combined test helps clinicians explore the connection between infection-driven immune responses and autoimmune reactivity.

The IgG Outer Surface Proteins A and C (OspA & OspC) test is a blood test that measures your immune system’s production of IgG antibodies against specific proteins on the surface of Borrelia burgdorferi, the bacteria that causes Lyme disease.

Outer Surface Proteins (Osp) are molecules the bacteria use to survive and infect humans:

• OspA helps the bacteria persist in ticks.

• OspC plays a key role in establishing infection in people.

When your immune system encounters Borrelia burgdorferi, it may produce IgG antibodies targeting these proteins. Detecting these antibodies can help provide clues about whether your body has mounted a response to Lyme disease.

The IgG OspE test measures antibodies against Outer Surface Protein E (OspE) of Borrelia burgdorferi, one of the proteins that help the bacterium evade the immune system and persist in the body. OspE belongs to the Erp (OspE-related proteins) family, which plays a key role in protecting Borrelia from complement-mediated killing by binding to host factor H.

The IgG VmpE test measures antibodies against Variable Major Protein E (VmpE), a surface protein produced by Borrelia burgdorferi, the bacterium that causes Lyme disease. VmpE belongs to a family of variable major proteins (Vmps) that the bacteria can change through a process called antigenic variation. This ability allows Borrelia to evade immune detection and sometimes persist in the body.

IgG (Immunoglobulin G) is a vital part of your immune defense system. Abnormal levels—either too high or too low—can be a sign of chronic infection, autoimmune activity, immune deficiency, or other systemic conditions. Whether you're experiencing frequent infections or unexplained inflammation, this test offers critical insight into how your immune system is functioning and what steps may be needed next.

IgG, Quant, CSF stands for Immunoglobulin G, Quantitative, Cerebrospinal Fluid. This test measures the concentration of IgG, a type of antibody, in your cerebrospinal fluid (CSF)—the clear fluid that surrounds your brain and spinal cord.

What is IgG?

Immunoglobulin G (IgG) is the most abundant antibody in the body. It plays a critical role in immune defense by identifying and neutralizing viruses, bacteria, and other foreign substances. IgG is normally found in the blood but can also be present in small amounts in the CSF.

IgG is a combination of four slightly different types of IgG called IgG subclasses: IgG1, IgG2, IgG3 and IgG4. When one or more of these subclasses is persistently low and total IgG is normal, a subclass deficiency is present.

IgG2 is one of the four subclasses of total IgG, and it specializes in antibodies against the sugar coats of encapsulated bacteria like pneumococcus and Haemophilus. The finding that carries weight is a low IgG2 — but the number alone decides little. A single low subclass result is insufficient: levels vary over time and between laboratories, so an abnormal value is confirmed on a later sample and read together with two other things — whether recurrent bacterial infections are documented, and whether the antibody response to a pneumococcal vaccine is poor. Those three lining up, not the depth of the number, are what make a low IgG2 clinically significant. A high IgG2, by contrast, is not established by the available sources as a diagnosis in its own right; it is read from the broader clinical picture. IgG2 is interpreted as part of the subclass panel and against age, since the IgG2 response matures slowly in childhood.

IgG is a combination of four slightly different types of IgG called IgG subclasses: IgG1, IgG2, IgG3 and IgG4. When one or more of these subclasses is persistently low and total IgG is normal, a subclass deficiency is present.

IgG is a combination of four slightly different types of IgG called IgG subclasses: IgG1, IgG2, IgG3 and IgG4. When one or more of these subclasses is persistently low and total IgG is normal, a subclass deficiency is present.

The IgG Synthesis Rate (CSF) measures how much immunoglobulin G (IgG) is being actively produced within the central nervous system (CNS)—specifically the brain and spinal cord. It helps determine whether the immune system is generating antibodies inside the CNS, which can signal inflammation, infection, or autoimmune activity affecting the brain or spinal cord.

Why it matters:
While some IgG naturally crosses from the blood into the cerebrospinal fluid (CSF), an elevated IgG synthesis rate means the immune system is producing extra IgG locally within the CNS. This is a hallmark of conditions like multiple sclerosis (MS), chronic CNS infections, or autoimmune neuroinflammatory diseases.