Borrelia IgM (Lyme disease)

The test measures IgM antibodies to Borrelia as one component of serological investigation of Lyme disease. IgM may be detected early in the immune response, but its diagnostic usefulness depends on symptom duration. Testing is used within an appropriate algorithm with confirmatory stages, not as a universal test after every tick bite.

An isolated positive IgM result in someone with prolonged symptoms is particularly prone to misinterpretation. Cross-reactions are possible, while antibodies may still be absent at the very start of illness. The doctor assesses the result together with symptoms, medical history and other investigations. The reference values of the individual laboratory are used for comparison, and changes over time are considered during follow-up.

• Investigate IgM at an appropriate time when Lyme disease is suspected.
• Complement multistep diagnosis ordered by a doctor.