title: Single radial haemolysis compared to haemagglutinin inhibition and microneutralization as a correlate of protection against influenza A H3N2 in children and adolescents.
abstract: Serum antibodies are often used as correlates of protection for influenza. Three commonly used serological assays for detecting influenza-specific serum antibodies are single radial haemolysis (SRH), haemagglutinin inhibition (HAI) and microneutralization (MN). However, here are limited data on SRH as well as HAI and MN as correlates of protection against influenza in children and adolescents. There are also limited data that compare SRH to HAI and MN.
  
  
  
  We sought primarily to understand how SRH titres correlate to protection against influenza infection in children and adolescents. We also compare SRH to HAI and MN.
  
  
  
  Of 732 healthy Hutterite children and adolescents aged between 3 and 15 years were enrolled from Saskatchewan and Alberta, Canada, in the 2008-2009 flu season. Blood samples were drawn from participants at baseline and between 3 and 5 weeks post-vaccination. Serum antibodies against seasonal H3N2 influenza were measured by SRH, HAI and MN assays.
  
  
  
  The estimates of protective efficacy fluctuated when the cut-off SRH values increased. The correlation between HAI and SRH titres was 0.53 (P<.01); between MN and SRH 0.82 (P<.01); and between HAI and MN 0.50 (P<.01). Sixteen per cent of participants had SRH titres below the detection limit, compared to 7% and 34% for the MN and HAI assays.
  
  
  
  SRH had the worst correlation with protection against seasonal H3N2 in children and adolescents compared to MN and HAI. SRH, HAI and MN titres were significantly correlated with each other. SRH was less sensitive than MN but more sensitive than HAI.
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Biao
authors.initials: B
authors.lastname: Wang
authors.affiliation: Department of Community Health Sciences, Cumming School of Medicine, University of Calgary, Calgary, AB, Canada.
authors.forename: Margaret L
authors.initials: ML
authors.lastname: Russell
authors.affiliation: Research Institute of the McGill University Health Center, Montreal, QC, Canada.
authors.forename: Angela
authors.initials: A
authors.lastname: Brewer
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Newton
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.
authors.forename: Pardeep
authors.initials: P
authors.lastname: Singh
authors.affiliation: Research Institute of the McGill University Health Center, Montreal, QC, Canada.
authors.forename: Brian J
authors.identifier: 0000-0003-3251-958X
authors.initials: BJ
authors.lastname: Ward
authors.affiliation: Department of Pathology and Molecular Medicine, McMaster University, Hamilton, ON, Canada.|Department of Medicine, McMaster University, Hamilton, ON, Canada.|Department of Clinical Epidemiology and Biostatistics, McMaster University, Hamilton, ON, Canada.|Michael G. De- Groote Institute for Infectious Disease Research, McMaster University, Hamilton, ON, Canada.
authors.forename: Mark
authors.identifier: 0000-0003-2315-5390
authors.initials: M
authors.lastname: Loeb
mesh_terms: D000293:Adolescent; D000914:Antibodies, Viral / Q000276:immunology*; D002648:Child; D002675:Child, Preschool; D005260:Female; D006385:Hemagglutination Inhibition Tests / Q000379:methods*; D006461:Hemolysis; D006801:Humans; D053122:Influenza A Virus, H3N2 Subtype / Q000235:genetics / Q000276:immunology* / Q000302:isolation & purification; D007251:Influenza, Human / Q000097:blood / Q000821:virology*; D008297:Male; D009500:Neutralization Tests / Q000379:methods*
chemical_list: D000914:Antibodies, Viral
keywords: children and adolescents; correlate of protection; haemagglutinin inhibition; influenza A H3N2; microneutralization; single radial haemolysis