title: The value of CMV IgG avidity and immunoblot for timing the onset of primary CMV infection in pregnancy.
abstract: BACKGROUND
  Primary CMV infections in pregnancy are usually asymptomatic and only detected by serology. Estimating the onset of infection is a major diagnostic goal, since primary infections around conception and in early gestation hold a higher risk for congenital disease than those in later pregnancy.
  
  
  OBJECTIVE
  To assess the ability of serological supplementary CMV assays to date the onset of primary infection.
  
  
  METHODS
  From our routine diagnosis we identified 61 pregnant women (n=188 serum samples) with precisely determined onset of CMV primary infection either by IgG seroconversion (n=24) or by significant IgG antibody rise (n=37). One hundred and forty-seven sera were investigated using the VIDAS(®) CMV IgG avidity EIA (BioMèrieux) and 83 sera using the recomBlot CMV IgG with avidity (Mikrogen).
  
  
  RESULTS
  Both assays proofed to be reliable in terms of timing the onset of CMV primary infection. An avidity index (AI) in the VIDAS avidity EIA of <40% indicated primary infection within the last 20 weeks (positive predictive value 93.4%; 99/106), whereas an intermediate AI excluded primary infection within the last 12 weeks (negative predictive value 88.2%; 15/17). The recomBlot showed high reliability (PPV 96.9%; 31/33) for timing the onset of infection within the last 14 weeks. Avidity testing by blot however could not be interpreted in 11 of 47 sera (23.4%).
  
  
  CONCLUSIONS
  For timing the onset of infection (before or in early pregnancy) CMV avidity testing is most helpful if carried out within the first trimester up to the beginning of second trimester.
authors.affiliation: Institute für Virology, Infektiologie und Epidemiologie e.V., Vorsitzende G. Enders, Labor Enders, Prof. Dr. med. Gisela Enders & Kollegen MVZ, Rosenbergstraße 85, D-70193 Stuttgart, Germany. enders@labor-enders.de
authors.forename: Gisela
authors.initials: G
authors.lastname: Enders
authors.forename: Anja
authors.initials: A
authors.lastname: Daiminger
authors.forename: Ursula
authors.initials: U
authors.lastname: Bäder
authors.forename: Simone
authors.initials: S
authors.lastname: Exler
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Schimpf
authors.forename: Martin
authors.initials: M
authors.lastname: Enders
mesh_terms: D000914:Antibodies, Viral / Q000276:immunology*; D000915:Antibody Affinity; D019411:Clinical Laboratory Techniques / Q000379:methods*; D003586:Cytomegalovirus Infections / Q000175:diagnosis* / Q000276:immunology; D005260:Female; D006801:Humans; D007074:Immunoglobulin G / Q000276:immunology*; D011247:Pregnancy; D011251:Pregnancy Complications, Infectious / Q000175:diagnosis* / Q000276:immunology; D012698:Serologic Tests / Q000379:methods; D013997:Time Factors
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G