The IgG Babesia test measures antibodies against Babesia species, a group of parasites transmitted by ticks that can cause babesiosis, a malaria-like illness. Babesia microti is the most common species in North America, while Babesia divergens and others are more frequently found in Europe and Asia.

What IgG Babesia Means

• IgG antibodies typically develop several weeks after infection and may remain detectable for months or years, even after treatment.

• A positive IgG result usually indicates past exposure or immune memory, not necessarily an active infection.

• IgM antibodies are more reflective of recent or acute babesiosis, while IgG testing provides a view of longer-term immune response.

The IgG Bartonella test measures antibodies against Bartonella species, a group of bacteria transmitted by ticks, fleas, or scratches from infected animals (especially cats). Bartonella henselae and Bartonella quintana are the most common human pathogens. Infection can lead to cat scratch disease, trench fever, or tick-borne bartonellosis, which may cause persistent systemic or neurological symptoms.

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.

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.

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.

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.

The IgG/Alb Ratio, CSF helps distinguish whether elevated IgG in the cerebrospinal fluid is due to local immune activity or simply leakage through a damaged blood-brain barrier. A high ratio often points to neurological conditions like multiple sclerosis or chronic CNS infections. A normal or low ratio suggests stable immune activity and barrier integrity.

IgM B. afzelii measures early antibodies against Borrelia afzelii, a major cause of Lyme disease in Europe and Asia. Unlike B. burgdorferi sensu stricto, which dominates in North America, B. afzelii is strongly linked to skin-related forms of Lyme borreliosis, including erythema migrans and acrodermatitis chronica atrophicans (ACA). IgM antibodies typically appear within the first weeks of infection, making this marker useful for detecting recent or early exposure, especially in patients with skin or joint symptoms after tick bites. Because low-level or isolated IgM responses can reflect cross-reactivity or false positives, results should always be interpreted with other Borrelia markers, clinical history, and follow-up testing.

If your result is Equivocal or Borderline (close to the cut-off):

What it means: Borderline levels of IgM antibodies were detected against Borrelia afzelii. This may represent an early or low-level immune response, or it may reflect non-specific reactivity rather than true Lyme infection. Results in this range require careful interpretation, particularly if you have Lyme-like symptoms or known tick exposure.

Next steps: Your doctor may recommend repeat testing after a few weeks, reviewing other Lyme antibody markers (including B. burgdorferi and B. garinii), or confirming with an immunoblot. Clinical history and symptoms are essential to determine whether this finding represents Lyme disease.

Next Steps for an Equivocal Result

• Repeat testing: Because IgM antibodies may rise in the early weeks after infection, repeating the test in 2–4 weeks can help clarify whether the immune response is increasing (suggesting infection) or fading (suggesting no infection).

• Additional Lyme tests: Your doctor may order IgG antibody testing, immunoblots, or a broader Lyme panel (including other Borrelia subspecies and Osp proteins) to confirm the result.

• Consider co-infections: If exposure risk is high, testing for tick-borne co-infections (e.g., Babesia, Bartonella, Ehrlichia) may also be recommended.

• Clinical evaluation: Symptoms and history of tick exposure are critical. Even borderline results can be significant if you have classic Lyme signs such as erythema migrans, joint pain, neurological changes, or unexplained fatigue.

• Ongoing monitoring: If symptoms persist but results remain unclear, your provider may recommend ongoing monitoring and possibly other diagnostic methods such as PCR.

The IgM B. burgdorferi sensu stricto test helps detect early Lyme disease by measuring IgM antibodies, which the body produces soon after a tick bite. A positive result may point to a recent infection, but it isn’t always proof of active disease because false positives and lingering IgM can occur. Doctors use this test along with symptoms (such as rash, fever, tiredness, joint or nerve problems) and exposure history to make an accurate diagnosis. Finding Lyme disease early is important, since timely treatment can prevent serious complications affecting the joints, nervous system, or heart.

The IgM B. burgdorferi Antigen (AG) test measures early antibodies against a broad set of Borrelia burgdorferi proteins, making it a sensitive marker for detecting early Lyme disease. IgM antibodies typically appear within 1–2 weeks after a tick bite and peak in the first month, so a positive result may indicate a recent or active infection. However, IgM alone is not diagnostic: results can persist after treatment or arise from cross-reactions with other infections or autoimmune conditions. Therefore, this marker is most valuable when interpreted with symptoms, exposure history, IgG results, and confirmatory tests. As part of a comprehensive Lyme serology panel, the IgM AG test supports early recognition and management of Lyme disease, helping to prevent progression to later complications affecting joints, the nervous system, or the heart.

An equivocal result means your IgM antibody level is right at the borderline — not clearly negative, but not strongly positive either. This does not confirm Lyme disease. Sometimes this happens if the test is done very soon after a tick bite, before antibodies fully develop, or because of background signals in the immune system. Your doctor may suggest repeating the test after a few weeks, checking for other antibodies, and reviewing your symptoms and history before making any diagnosis.

The IgM B. garinii test detects early antibodies against Borrelia garinii, a subspecies within the Borrelia burgdorferi sensu lato complex that is especially common in Europe and Asia and strongly associated with neurological forms of Lyme disease (neuroborreliosis). IgM antibodies typically appear 1–3 weeks after infection, making this marker useful for identifying recent immune responses in patients with early neurological symptoms such as meningitis, facial nerve palsy, radiculoneuritis, or cognitive issues. While a positive result may support an early diagnosis, interpretation depends on clinical context, timing, and geography, since false positives and persistent IgM without IgG conversion can occur. The test is most informative when combined with other Lyme markers (e.g., B. burgdorferi sensu stricto, B. afzelii, or Osp proteins), helping clinicians recognize neurological Lyme disease earlier and guide appropriate management.

An equivocal result means the test is in the borderline range — not clearly negative, but not fully positive either. This can happen if testing is done very early after a tick bite, before antibodies have built up, or if the signal comes from the immune system reacting to something else. On its own, this result does not confirm or rule out Lyme disease. Your doctor may recommend repeating the test, checking other Lyme markers, and reviewing your symptoms and travel or exposure history to get a clearer answer.