Significance of avidity and immunoblot analysis for rubella IgM-positive serum samples in pregnant women

J Virol Methods. 2005 Dec;130(1-2):66-71. doi: 10.1016/j.jviromet.2005.06.004. Epub 2005 Jul 15.

Abstract

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.

MeSH terms

  • Adult
  • Antibodies, Viral / blood*
  • Antibody Affinity
  • Blotting, Western*
  • Female
  • Glycoproteins / immunology
  • Humans
  • Immunoglobulin G / blood*
  • Immunoglobulin G / immunology
  • Immunoglobulin M / blood*
  • Pregnancy
  • Pregnancy Complications, Infectious / diagnosis*
  • Rubella / diagnosis*
  • Rubella virus / immunology*
  • Viral Envelope Proteins / immunology

Substances

  • Antibodies, Viral
  • Glycoproteins
  • Immunoglobulin G
  • Immunoglobulin M
  • Viral Envelope Proteins