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[False rubella diagnosis in pregnancy by IgM enzyme immunoassay]
T Grüninger1, W Wunderli, A E Böhlen-Bodmer
1Maternité Inselhof Triemli, Zürich, Schweiz.
Abstract:
On the basis of a case report of a false-positive rubella diagnosis in early pregnancy the interpretation of positive IgM is discussed. A primigravida at 14 weeks of gestation showed rubella-specific IgM in an enzyme immunoassay. This result could not be confirmed by an alternative method (hemagglutination-inhibiting test after separating the serum by density gradients into different immunoglobulin classes and removal of the IgG with protein A). The immunological status corresponded with a past rubella infection or with the status after vaccination (IgG-positive). It is therefore recommended to use an additional method in the presence of IgM, especially if an interruption of the pregnancy has to be considered. In the course of the examination a recent cytomegalovirus infection could be detected.
Insights
A false-positive rubella diagnosis in early pregnancy highlights the need for confirmatory testing. Always use an additional method for rubella IgM testing, especially when pregnancy decisions are involved.
Area of Science:
- Immunology
- Virology
- Obstetrics
Background:
- Accurate diagnosis of rubella infection during pregnancy is crucial for management decisions.
- Rubella-specific IgM antibodies are often used as an indicator of recent infection.
Observation:
- A primigravida at 14 weeks gestation presented with a positive rubella IgM result via enzyme immunoassay.
- This positive IgM result could not be confirmed by a secondary method, such as a hemagglutination-inhibiting test.
Findings:
- The patient's immunological status indicated past rubella infection or vaccination (IgG-positive).
- The initial positive IgM result was deemed a false positive, underscoring potential diagnostic limitations.
Implications:
- Confirmatory testing is essential when interpreting positive rubella IgM results in pregnant patients.
- Additional diagnostic methods should be employed, particularly when considering pregnancy termination based on rubella diagnosis.
- Concurrent cytomegalovirus infection was identified during the diagnostic workup.