title: Sensitivity and specificity of three ELISA-based assays for discriminating primary from secondary acute dengue virus infection.
abstract: BACKGROUND
  Discrimination between primary and secondary dengue virus infection traditionally has been performed using the hemagglutination inhibition (HI) test. However, this test has practical limitations and disadvantages.
  
  
  OBJECTIVE
  To evaluate the ability of three ELISA-based methods (IgG avidity test, IgM/IgG ratio and IgG titer) to discriminate primary from secondary dengue infection.
  
  
  METHODS
  Serum samples from convalescent-phase patients with confirmed acute, primary (n=46) or secondary (n=33) dengue virus infection were tested using three ELISA-based methods. A ROC curve was employed to establish the cut-off points and to evaluate the ability of the three methods to distinguish between acute, primary and secondary dengue virus infection.
  
  
  RESULTS
  All three assays exhibited sensitivity and negative predictive values of 100% for defining secondary infection. The specificity and positive predictive values were respectively 97.8% and 93.7% for the IgG avidity test, 95.7% and 88.2% for the IgM/IgG ratio assays, and 97.8% and 93.7% for the IgG titer assay.
  
  
  CONCLUSIONS
  All three ELISA-based assays proved reliable tools for discriminating between acute, primary and secondary dengue virus infection when using serum samples from convalescent-phase patients.
authors.affiliation: Laboratório de Virologia (LIM-HC)--Instituto de Medicina Tropical de São Paulo e Departamento de Moléstias Infecciosas e Parasitárias da Faculdade de Medicina, Universidade de São Paulo, São Paulo, SP, Brazil.
authors.forename: Vanda Akico Ueda Fick
authors.initials: VA
authors.lastname: de Souza
authors.forename: Adriana Fumie
authors.initials: AF
authors.lastname: Tateno
authors.forename: Renato Reis
authors.initials: RR
authors.lastname: Oliveira
authors.forename: Renan B
authors.initials: RB
authors.lastname: Domingues
authors.forename: Evaldo Stanislau
authors.initials: ES
authors.lastname: Araújo
authors.forename: Gustavo W
authors.initials: GW
authors.lastname: Kuster
authors.forename: Cláudio Sérgio
authors.initials: CS
authors.lastname: Pannuti
mesh_terms: D000208:Acute Disease; D000914:Antibodies, Viral / Q000097:blood*; D000915:Antibody Affinity; D003289:Convalescence; D003715:Dengue / Q000175:diagnosis* / Q000276:immunology / Q000503:physiopathology / Q000821:virology; D003716:Dengue Virus / Q000276:immunology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M