title: Assessing Immunity to Rubella Virus: a Plea for Standardization of IgG (Immuno)assays.
abstract: Immunity to rubella virus (RV) is commonly determined by measuring specific immunoglobulin G (RV IgG). However, RV IgG results and their interpretation may vary, depending on the immunoassay, even though most commercial immunoassays (CIAs) have been calibrated against an international standard and results are reported in international units per milliliter. A panel of 322 sera collected from pregnant women that tested negative or equivocal for RV IgG in a prior test (routine screening) was selected. This panel was tested with two reference tests, immunoblotting (IB) and neutralization (Nt), and with 8 CIAs widely used in Europe. IB and Nt gave concordant results on 267/322 (82.9%) sera. Of these, 85 (26.4%) sera were negative and 182 (56.5%) sera were positive for both tests. All 85 IB/Nt-negative samples were classified as negative with all CIAs. Of the 182 IB/Nt-positive samples, 25.3 to 61.5% were classified as equivocal and 6 to 64.8% were classified as positive with the CIAs. Wide variations in titers in international units per milliliter were observed. In our series, more than half of the women considered susceptible to RV based on CIA results tested positive for RV antibodies by IB/Nt. Our data suggest that (i) sensitivity of CIAs could be increased by considering equivocal results as positive and (ii) the definition of immunity to RV as the 10-IU/ml usual cutoff as well as the use of quantitative results for clinical decisions may warrant reconsideration. A better standardization of CIAs for RV IgG determination is needed.
authors.affiliation: AP-HP, Hôpital Paul Brousse, Groupe Hospitalier Universitaire Paris-Sud, Virologie, WHO Rubella NRL, National Reference Laboratory for Maternofetal Rubella Infections, University Paris-Sud, INSERM U1193, Villejuif, France.
authors.forename: Elise
authors.initials: E
authors.lastname: Bouthry
authors.affiliation: Fondazione IRCCS Policlinico San Matteo, SC Microbiologia e Virologia, Pavia, Italy m.furione@smatteo.pv.it christelle.vauloup@aphp.fr.
authors.forename: Milena
authors.initials: M
authors.lastname: Furione
authors.affiliation: Institute of Virology, University Medical Center Freiburg, Freiburg, Germany.
authors.forename: Daniela
authors.initials: D
authors.lastname: Huzly
authors.affiliation: Measles, Mumps, Rubella and Herpesvirus Laboratory Branch, Division of Viral, Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Adaeze
authors.initials: A
authors.lastname: Ogee-Nwankwo
authors.affiliation: Measles, Mumps, Rubella and Herpesvirus Laboratory Branch, Division of Viral, Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: LiJuan
authors.initials: L
authors.lastname: Hao
authors.affiliation: Measles, Mumps, Rubella and Herpesvirus Laboratory Branch, Division of Viral, Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Adebola
authors.initials: A
authors.lastname: Adebayo
authors.affiliation: Measles, Mumps, Rubella and Herpesvirus Laboratory Branch, Division of Viral, Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Icenogle
authors.affiliation: Fondazione IRCCS Policlinico San Matteo, SC Microbiologia e Virologia, Pavia, Italy.
authors.forename: Antonella
authors.initials: A
authors.lastname: Sarasini
authors.affiliation: Fondazione IRCCS Policlinico San Matteo, SC Ostetricia e Ginecologia, Pavia, Italy.
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Revello
authors.affiliation: AP-HP, Hôpital Paul Brousse, Groupe Hospitalier Universitaire Paris-Sud, Virologie, WHO Rubella NRL, National Reference Laboratory for Maternofetal Rubella Infections, University Paris-Sud, INSERM U1193, Villejuif, France.
authors.forename: Liliane
authors.initials: L
authors.lastname: Grangeot-Keros
authors.affiliation: AP-HP, Hôpital Paul Brousse, Groupe Hospitalier Universitaire Paris-Sud, Virologie, WHO Rubella NRL, National Reference Laboratory for Maternofetal Rubella Infections, University Paris-Sud, INSERM U1193, Villejuif, France m.furione@smatteo.pv.it christelle.vauloup@aphp.fr.
authors.forename: Christelle
authors.initials: C
authors.lastname: Vauloup-Fellous
mesh_terms: D000328:Adult; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000592:standards*; D007074:Immunoglobulin G / Q000097:blood*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000517:prevention & control*; D012409:Rubella / Q000517:prevention & control*; D012412:Rubella virus / Q000276:immunology*
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G