What does a positive Immunoglobulin G (IgG) and negative Immunoglobulin M (IgM) for Borrelia burgdorferi indicate in a patient?

From the Guidelines

A positive IgG and negative IgM for Borrelia burgdorferi typically indicates past or late-stage Lyme disease infection rather than an acute infection. This pattern suggests the patient was infected with the Lyme disease bacterium in the past, likely more than 4-6 weeks ago, and their immune system has already developed long-term antibodies while the early-response antibodies have declined. IgM antibodies appear first during infection (within 1-2 weeks) but generally decrease after 4-6 weeks, while IgG antibodies develop more slowly but persist for months to years after infection 1.

Clinical Interpretation

This serological pattern alone is not sufficient for diagnosis and should be interpreted alongside clinical symptoms and exposure history. If the patient has ongoing symptoms consistent with late Lyme disease (such as arthritis, neurological issues, or cardiac abnormalities), treatment with appropriate antibiotics may be warranted. According to the guidelines by the Infectious Diseases Society of America 1, standard treatment for late Lyme disease typically involves:

• Doxycycline 100mg twice daily for 2-4 weeks for patients without neurologic disease
• Alternatives like amoxicillin or ceftriaxone depending on manifestations and contraindications
• For patients with arthritis without neurologic disease, oral regimen for 28 days is recommended

Treatment Considerations

However, if the patient is asymptomatic, this serological finding may simply represent a past, resolved infection that requires no treatment. It's essential to consider the patient's clinical presentation, medical history, and potential for antibiotic resistance when deciding on a treatment plan. As noted in the guidelines 1, complete response to treatment may be delayed beyond the treatment duration, and relapse may occur with any of these regimens.

Key Points

• A positive IgG and negative IgM for Borrelia burgdorferi indicates past or late-stage Lyme disease infection
• Clinical symptoms and exposure history should be considered alongside serological results for diagnosis
• Treatment with antibiotics may be warranted for patients with ongoing symptoms consistent with late Lyme disease
• Asymptomatic patients may not require treatment if the serological finding represents a past, resolved infection

From the Research

Interpretation of IgG and IgM Test Results for Borrelia burgdorferi

• A positive Immunoglobulin G (IgG) and negative Immunoglobulin M (IgM) test result for Borrelia burgdorferi indicates that the patient has been exposed to the bacteria at some point in the past 2.
• IgG antibodies typically appear later in the course of the infection and can persist for months or even years after the infection has been cleared 3, 4.
• A negative IgM result suggests that the patient is not in the early stages of the infection, as IgM antibodies are typically present during the initial stages of the disease 4.
• It is essential to interpret serological results in the context of clinical signs and symptoms, as false-positive and false-negative results can occur 4.

Clinical Implications

• The presence of positive IgG antibodies without clinical symptoms may indicate a past infection that has been cleared 5.
• However, it is also possible that the patient has a chronic or persistent infection, and further evaluation and treatment may be necessary 2.
• The patient's medical history, physical examination, and other diagnostic tests should be considered when interpreting the test results 6.

Limitations of Serological Testing

• Serological testing for Borrelia burgdorferi has limitations, including the potential for false-positive and false-negative results 3, 4.
• The tests may not be standardized, and results may vary depending on the laboratory and testing methods used 4.
• Clinical judgment and consideration of other diagnostic factors are essential when interpreting serological results 6, 4.