title: Predictors of influenza among older adults in the emergency department.
abstract: BACKGROUND
  Diagnosis of influenza in older adults may be complicated by atypical presentations or when patients present with complications of an underlying illness. We aimed to identify clinical characteristics and epidemiological factors associated with influenza among community-dwelling adults aged ≥60 years presenting to emergency departments.
  
  
  METHODS
  We identified patients with influenza-compatible chief complaints presenting to emergency departments of six acute care hospitals in Ontario, Canada during the 2011/12 and 2012/13 influenza seasons. Clinical characteristics, medical history and demographics were collected by patient interview, chart review and by contacting vaccine providers. Nasopharyngeal swabs were tested for influenza using polymerase chain reaction. We modeled predictors of influenza using multivariable logistic regression models that compared individuals with and without influenza.
  
  
  RESULTS
  Of 1318 participants, 151 (11 %) had influenza (98 A/H3N2, 12 A/H1N1, 4 A [not sub-typed], 37 B). In the multivariable model, clinical symptoms associated with influenza were cough (OR 6.4, 95 % CI 3.2, 13.0), feverishness and/or triage temperature ≥37.2 °C (OR 3.0, 95 % CI 2.0, 4.7), 2-5 days from symptom onset to the emergency department visit (OR 2.2, 95 % CI 1.5, 3.2), and wheezing (OR 2.1, 95 % CI 1.3, 3.3). The effect of cough on influenza increased with older age. Epidemiological factors associated with increased odds for influenza included weeks when ≥10 % influenza tests from provincial laboratories were positive (OR 5.1, 95 % CI 1.2, 21.7) and exposure to a person with influenza-like illness (OR 1.9, 95 % CI 1.3, 2.8). Among participants with influenza, only 47 (31 %) met the U.S. Centers for Disease Control and Prevention criteria for influenza-like illness (temperature ≥37.8 °C and cough and/or sore throat).
  
  
  CONCLUSIONS
  As in younger adults, cough and feverishness are the two symptoms most predictive of influenza in the elderly. Current influenza-like illness definitions did not adequately capture influenza in older adults.
authors: Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada. popo.lam@utoronto.ca.|Department of Microbiology, Mount Sinai Hospital, Toronto, ON, Canada. popo.lam@utoronto.ca.
authors: Po-Po
authors: http://orcid.org/0000-0003-3125-9958
authors: PP
authors: Lam
authors: Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.|Department of Microbiology, Mount Sinai Hospital, Toronto, ON, Canada.
authors: Brenda L
authors: BL
authors: Coleman
authors: Department of Microbiology, Mount Sinai Hospital, Toronto, ON, Canada.|Toronto Invasive Bacterial Diseases Network, Toronto, ON, Canada.
authors: Karen
authors: K
authors: Green
authors: Toronto East General Hospital, Toronto, ON, Canada.
authors: Jeff
authors: J
authors: Powis
authors: William Osler Health System, Toronto, ON, Canada.
authors: David
authors: D
authors: Richardson
authors: North York General Hospital, Toronto, ON, Canada.
authors: Kevin
authors: K
authors: Katz
authors: Schwartz/Reisman Emergency Medicine Institute, Mount Sinai Hospital, Toronto, ON, Canada.
authors: Bjug
authors: B
authors: Borgundvaag
authors: Department of Emergency Medicine, University Health Network, Toronto, ON, Canada.
authors: Telisha
authors: T
authors: Smith-Gorvie
authors: Institute for Clinical Evaluative Sciences, Toronto, ON, Canada.
authors: Jeffrey C
authors: JC
authors: Kwong
authors: Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.
authors: Susan J
authors: SJ
authors: Bondy
authors: Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada.|Department of Microbiology, Mount Sinai Hospital, Toronto, ON, Canada.|Toronto Invasive Bacterial Diseases Network, Toronto, ON, Canada.
authors: Allison
authors: A
authors: McGeer
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D003371:Cough / Q000209:etiology; D004636:Emergency Service, Hospital / Q000706:statistics & numerical data; D005260:Female; D005334:Fever / Q000209:etiology; D006801:Humans; D053118:Influenza A Virus, H1N1 Subtype / Q000472:pathogenicity; D053122:Influenza A Virus, H3N2 Subtype / Q000472:pathogenicity; D007252:Influenza Vaccines / Q000627:therapeutic use; D007251:Influenza, Human / Q000453:epidemiology* / Q000209:etiology*; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D009864:Ontario; D010612:Pharyngitis / Q000209:etiology; D016133:Polymerase Chain Reaction
chemical_list: D007252:Influenza Vaccines
keywords: Clinical symptoms; Elderly; Influenza; Older adults