Arbiter of Doubts
IgM to rubella is often falsely positive or persists for years - avidity resolves the drama: high-avidity IgG with any IgM closes the issue in favor of safety. The test is taken immediately if the pregnant woman’s serology is controversial, before any decisions are made. Similar logic works for CMV and Toxoplasma.
When is it appointed?
- pregnancy planning - TORCH status;
- pregnancy - screening and clarification of doubtful results;
- decision to vaccinate against rubella;
- lymphadenopathy, prolonged low-grade fever - etiology;
- clarification of the stage of infection (avidity).
Reading antibodies correctly
IgM is a marker of a fresh infection (but often “phonitis” is false), IgG is immune memory and protection. For pregnancy, the ideal profile is “IgG+, IgM−” (there is immunity, there is no risk); “IgG−, IgM−” means vulnerability (rubella - vaccination BEFORE conception!); “IgM+” requires clarification by IgG avidity: high avidity = long-standing infection, no danger. A competent interpretation saves you from unnecessary fears and interventions - the clinic doctor will analyze your profile.
