title: Estimating sensitivity of laboratory testing for influenza in Canada through modelling.
abstract: BACKGROUND
  The weekly proportion of laboratory tests that are positive for influenza is used in public health surveillance systems to identify periods of influenza activity. We aimed to estimate the sensitivity of influenza testing in Canada based on results of a national respiratory virus surveillance system.
  
  
  RESULTS
  The weekly number of influenza-negative tests from 1999 to 2006 was modelled as a function of laboratory-confirmed positive tests for influenza, respiratory syncytial virus (RSV), adenovirus and parainfluenza viruses, seasonality, and trend using Poisson regression. Sensitivity was calculated as the number of influenza positive tests divided by the number of influenza positive tests plus the model-estimated number of false negative tests. The sensitivity of influenza testing was estimated to be 33% (95%CI 32-34%), varying from 30-40% depending on the season and region.
  
  
  CONCLUSIONS
  The estimated sensitivity of influenza tests reported to this national laboratory surveillance system is considerably less than reported test characteristics for most laboratory tests. A number of factors may explain this difference, including sample quality and specimen procurement issues as well as test characteristics. Improved diagnosis would permit better estimation of the burden of influenza.
authors.affiliation: Infectious Disease and Emergency Preparedness Branch, Public Health Agency of Canada, Ottawa, Ontario, Canada. Dena_Schanzer@phac-aspc.gc.ca
authors.forename: Dena L
authors.initials: DL
authors.lastname: Schanzer
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Garner
authors.forename: Todd F
authors.initials: TF
authors.lastname: Hatchette
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Langley
authors.forename: Samina
authors.initials: S
authors.lastname: Aziz
authors.forename: Theresa W S
authors.initials: TW
authors.lastname: Tam
mesh_terms: D002170:Canada / Q000453:epidemiology; D019411:Clinical Laboratory Techniques; D006801:Humans; D007251:Influenza, Human / Q000175:diagnosis / Q000453:epidemiology*; D008962:Models, Theoretical; D012621:Seasons; D012680:Sensitivity and Specificity
references.citation: Diagn Microbiol Infect Dis. 1986 Nov;5(4):307-12
references.pmid: 3536275
references.citation: Pediatr Infect Dis J. 2008 Oct;27(10 Suppl):S80-3
references.pmid: 18820584
references.citation: Clin Infect Dis. 2005 Sep 15;41(6):822-8
references.pmid: 16107980
references.citation: N Engl J Med. 2005 Dec 15;353(24):2559-67
references.pmid: 16354892
references.citation: J Clin Microbiol. 2003 Sep;41(9):4298-303
references.pmid: 12958260
references.citation: Euro Surveill. 2002 Dec;7(12):180-3
references.pmid: 12631984
references.citation: J Clin Microbiol. 2006 Jun;44(6):2265-7
references.pmid: 16757636
references.citation: Can J Public Health. 2009 May-Jun;100(3):204-7
references.pmid: 19507723
references.citation: J Clin Virol. 2007 Jun;39(2):132-5
references.pmid: 17452000
references.citation: J Infect. 2007 Sep;55(3):240-8
references.pmid: 17582503
references.citation: J Clin Virol. 2005 Jun;33(2):172-5
references.pmid: 15911434
references.citation: Influenza Other Respir Viruses. 2008 Jan;2(1):1-8
references.pmid: 19453488
references.citation: Pediatr Infect Dis J. 2006 Sep;25(9):795-800
references.pmid: 16940836
references.citation: Clin Microbiol Rev. 2006 Jan;19(1):165-256
references.pmid: 16418529
references.citation: Arch Intern Med. 2008 Dec 8;168(22):2489-96
references.pmid: 19064834
references.citation: J Clin Virol. 2004 Sep;31(1):40-5
references.pmid: 15288612
references.citation: J Clin Microbiol. 2007 Jul;45(7):2260-2
references.pmid: 17507513
references.citation: Clin Infect Dis. 2008 Apr 1;46(7):e61-4
references.pmid: 18444806
references.citation: J Clin Microbiol. 2002 Nov;40(11):4337-9
references.pmid: 12409425
references.citation: J Clin Microbiol. 2003 Oct;41(10):4642-6
references.pmid: 14532196
references.citation: J Obstet Gynaecol Can. 2007 Aug;29(8):622-9
references.pmid: 17714614
references.citation: Can Commun Dis Rep. 2007 Feb 1;33(3):21-41
references.pmid: 17323533
references.citation: Epidemiol Infect. 2007 Aug;135(6):951-8
references.pmid: 17156502
references.citation: Vaccine. 2008 Aug 26;26(36):4697-703
references.pmid: 18620016
references.citation: Clin Diagn Lab Immunol. 2005 Mar;12(3):367-70
references.pmid: 15753248
references.citation: Can Commun Dis Rep. 2005 Jan 1;31(1):1-18
references.pmid: 15645607
references.citation: Clin Infect Dis. 2007 Dec 15;45(12):1568-75
references.pmid: 18190317
references.citation: Pediatrics. 2007 Jan;119(1):e6-11
references.pmid: 17200259
references.citation: Epidemiol Infect. 2007 Oct;135(7):1109-16
references.pmid: 17306052
references.citation: CMAJ. 2002 Feb 19;166(4):445-6
references.pmid: 11873921
references.citation: JAMA. 2004 Sep 15;292(11):1333-40
references.pmid: 15367555
references.citation: J Clin Microbiol. 2003 Aug;41(8):3487-93
references.pmid: 12904343
references.citation: J Infect Dis. 2004 Feb 15;189(4):706-10
references.pmid: 14767825
references.citation: J Infect Dis. 2006 Nov 1;194 Suppl 2:S98-110
references.pmid: 17163396
references.citation: J Clin Microbiol. 2002 Jun;40(6):2051-6
references.pmid: 12037063