From the Guidelines
No, a negative Rubella Immunoglobulin G (IgG) test result does not necessarily indicate non-immunity to Rubella, as it may indicate that the individual has not been previously infected or vaccinated, or that their immune system is not producing a detectable level of IgG antibodies 1.
Key Considerations
- The presence of serum Rubella IgG is considered the only reliable evidence of previous Rubella infection 1
- A negative Rubella IgG test result may require a repeat test or a Rubella IgM test to confirm non-immunity
- If non-immunity is confirmed, vaccination with the Measles, Mumps, and Rubella (MMR) vaccine is recommended
- It is essential to consult a healthcare professional for personalized advice and guidance, as they can assess individual circumstances and provide tailored recommendations
Vaccination Recommendations
- The typical dose of the MMR vaccine is 0.5 mL administered subcutaneously
- A second dose may be given 4 weeks later if necessary, depending on individual circumstances and healthcare professional advice
From the Research
Interpretation of Rubella IgG Test Results
- A negative Rubella Immunoglobulin G (IgG) test result may not necessarily indicate non-immunity to Rubella, as evidenced by studies 2, 3.
- Research suggests that some individuals with negative Rubella IgG results may still have protective immunity against the virus 3.
- The sensitivity of commercial immunoassays (CIAs) for detecting Rubella IgG can vary, and considering equivocal results as positive may increase sensitivity 2.
Factors Affecting Rubella IgG Test Results
- The use of different immunoassays and reference tests can lead to variations in Rubella IgG test results 2, 4.
- The definition of immunity to Rubella as a 10-IU/ml cutoff may need to be reconsidered, and quantitative results may not be suitable for clinical decisions 2.
- Cell-mediated immunity, which is not routinely investigated, may also play a role in determining immunity to Rubella 3.
Diagnosis of Rubella Infection
- The avidity of IgG antibodies can help differentiate between primary Rubella infection and past infections or reinfections 5, 6.
- Glycoprotein-based IgM serology and immunoblot analysis can improve the specificity of diagnosing recent primary Rubella infections 6.
- Determining IgG avidity and analyzing anti-E2 IgG reactivity can help determine the time point of primary infection 6.