Significance of avidity and immunoblot analysis for rubella IgM-positive serum samples in pregnant women.
A total of 512 IgM-positive serum samples from 449 pregnant women referred by microbiologists and medical laboratories for additional testing and final interpretation were collected over a 3-year period. Employment of an IgM capture enzyme immunoassay (EIA) confirmed only 31% of the initial EIA-IgM-positive samples. In order to discriminate acute rubella virus infections, which are associated with increased risk of fetal infection and embryopathy, from persistent or non-specific IgM, IgG avidity index and the presence of IgG with specificity to rubella virus E2 glycoprotein was determined by Western immunoblot. In only six patients (1.3%), a primary infection with rubella virus was diagnosed on the basis of IgM positivity, low avidity IgG, absence of E2-specific IgG in immunoblot concordant with clinical findings as well as consistent changes in follow-up samples. The serological results were not compatible with rubella re-infection. The infection status in 14 patients (3.1%) remained inconclusive even when both avidity assay and immunoblot were used, while restriction to either test did not allow a conclusive interpretation in 11.6% of patients. The use of both assays is clearly better, and therefore, recommended in IgM-positive samples.
Hofmann
J
J
Institute of Virology, University of Leipzig, Johannisallee 30, 04103 Leipzig, Germany.
Liebert
U G
UG
D000328:Adult; D000914:Antibodies, Viral / Q000097:blood*; D000915:Antibody Affinity; D015153:Blotting, Western; D005260:Female; D006023:Glycoproteins / Q000276:immunology; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood* / Q000276:immunology; D007075:Immunoglobulin M / Q000097:blood*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis*; D012409:Rubella / Q000175:diagnosis*; D012412:Rubella virus / Q000276:immunology*; D014759:Viral Envelope Proteins / Q000276:immunology
D000914:Antibodies, Viral; D006023:Glycoproteins; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D014759:Viral Envelope Proteins