title: Low sensitivity of NS1 protein tests evidenced during a dengue type 2 virus outbreak in Santos, Brazil, in 2010.
abstract: In 2010, a large outbreak of dengue occurred in Santos, Brazil. The detection of the NS1 antigen was used for diagnosis in addition to the detection of IgG, IgM, and RNA. A large number of NS1 false-negative results were obtained. A total of 379 RNA-positive samples were selected for thorough evaluation. NS1 was reactive in 37.7% of cases. Most of the cases were characterized as a secondary infection by dengue 2 virus. Sequencing of NS1 positive and negative isolates did not reveal any mutation that could justify the diagnostic failure. Use of existing NS1 tests in the Brazilian population may present a low negative predictive value, and they should be used with caution, preferentially after performing a validation with samples freshly obtained during the ongoing epidemic.
authors.affiliation: Instituto de Medicina Tropical de São Paulo e Departamento de Moléstias Infecciosas e Parasitárias da Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Alvina Clara
authors.initials: AC
authors.lastname: Felix
authors.forename: Camila Malta
authors.initials: CM
authors.lastname: Romano
authors.forename: Cristiane de Campos
authors.initials: Cde C
authors.lastname: Centrone
authors.forename: Célia Lima
authors.initials: CL
authors.lastname: Rodrigues
authors.forename: Lucy
authors.initials: L
authors.lastname: Villas-Boas
authors.forename: Evaldo Stanislau
authors.initials: ES
authors.lastname: Araújo
authors.forename: Andréia Manso
authors.initials: AM
authors.lastname: de Matos
authors.forename: Karina Inácio
authors.initials: KI
authors.lastname: Carvalho
authors.forename: Celina Maria Turchi
authors.initials: CM
authors.lastname: Martelli
authors.forename: Esper Georges
authors.initials: EG
authors.lastname: Kallas
authors.forename: Claúdio Sérgio
authors.initials: CS
authors.lastname: Pannuti
authors.forename: José Eduardo
authors.initials: JE
authors.lastname: Levi
mesh_terms: D000914:Antibodies, Viral / Q000097:blood; D001938:Brazil / Q000453:epidemiology; D019411:Clinical Laboratory Techniques / Q000379:methods*; D003715:Dengue / Q000175:diagnosis* / Q000453:epidemiology*; D003716:Dengue Virus / Q000276:immunology / Q000302:isolation & purification*; D004196:Disease Outbreaks; D005188:False Negative Reactions; D006801:Humans; D007118:Immunoassay / Q000379:methods; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D012367:RNA, Viral / Q000097:blood; D012680:Sensitivity and Specificity; D017361:Viral Nonstructural Proteins / Q000032:analysis* / Q000276:immunology; D014773:Virology / Q000379:methods*
chemical_list: D000914:Antibodies, Viral; D007074:Immunoglobulin G; D007075:Immunoglobulin M; C079340:NS1 protein, Dengue virus type 2; D012367:RNA, Viral; D017361:Viral Nonstructural Proteins