Program Schedule

Predictors of Influenza Infection in Older Adults Presenting to Emergency Departments (EDs) in Toronto, Canada

Session: Poster Abstract Session: Clinical Respiratory Infections
Friday, October 10, 2014
Room: The Pennsylvania Convention Center: IDExpo Hall BC
  • 2014-10-03 ID week poster OED study-final.pdf (895.6 kB)
  • Background: Diagnosis of influenza in the elderly may be complicated by atypical presentations. We compared the characteristics of community-dwelling adults aged ≥60 years presenting to EDs during the 2011/12 and 2012/13 influenza seasons.

    Methods: We identified patients presenting to six EDs with influenza-compatible symptoms. Clinical characteristics, medical history and demographics were collected by patient interview, chart review and from vaccine providers. NP swabs were tested for flu using PCR. We modeled predictors of flu using multivariable logistic regression models that compared cases to test negative controls.

    Results: Of 1318 participants, 151 (11%) had flu (98 AH3N2, 12 AH1N1, 4 A(not subtyped), 37 B). In multivariable models, factors associated with flu were cough (A: OR 4.00, 95%CI 1.67-9.60; B: OR 10.4, 95%CI 2.35-45.8), feverishness and/or T≥37.20C  (A: OR 3.81, 95%CI 2.22-6.54; B: 2.36, 95%CI 1.02-5.47),  symptom duration of 2-5d (A: OR 2.15, 95%CI 1.35-3.43; B: OR 2.27, 95%CI 1.05-4.94) and level of flu in the community (A: OR 1.04, 95%CI 1.00-1.07; B: OR 1.13, 95%CI 1.08-1.19). The CDC ILI definition identified 47 (31%) flu cases. Additional factors associated with flu A included having any respiratory symptom (OR 2.29, 95%CI 1.22-4.23), working with children (OR 12.3, 95%CI 2.50-60.7), recent exposure to ILI (OR 1.74, 95%CI 1.08-2.83) and older age (OR 1.03, 95%CI 1.00-1.05). Confusion was associated with flu B among those not frail at baseline. As age increased, cough was more predictive of flu A and B.

    Conclusion: Cough and fever are as predictive of flu in the elderly as in younger adults but standard case definitions miss most patients. Adding epidemiological factors may be helpful for flu diagnoses. 

    Table. Characteristics of participants with no flu, flu A and flu B (n=1318)


    No Flu

    Flu A

    Flu B















    Feverishness/T >=37.20C







    Symptom onset 2-5 days prior







    Any respiratory symptom







    Any systemic symptom














    Exposure to person with ILI







    Influenza vaccination







    Working with children







    Age(yrs), median

    76 (IQR 16)

    77 (IQR 16)

    78 (IQR 17)

    % Positive flu tests, all labs, median

    21 (IQR 15)

    *29 (IQR 13)

    26 (IQR 13)

    *p<0.05 when compared against no flu

    Po-Po Lam, MSc1,2, Karen Green, MSc2,3, Brenda L. Coleman, PhD1,2, Jeff Powis, MD, MSc, FRCPC4, David Richardson, MD5, Kevin Katz, MD CM, MSc6, Bjug Borgundvaag, MD2, Telisha Smith-Gorvie, MD, MSc, FRCPC7, Jeffrey C. Kwong, MD8, Susan Bondy, PhD1 and Allison Mcgeer, MD, FRCPC1,2, (1)Dalla Lana School of Public Health, University of Toronto, Toronto, ON, Canada, (2)Mount Sinai Hospital, Toronto, ON, Canada, (3)Toronto Invasive Bacterial Diseases Network, Toronto, ON, Canada, (4)Toronto East General Hospital, Toronto, ON, Canada, (5)William Osler Health System, Brampton, ON, Canada, (6)North York General Hospital, Toronto, ON, Canada, (7)University Health Network, Toronto, ON, Canada, (8)Institute for Clinical Evaluative Sciences, Toronto, ON, Canada


    P. P. Lam, None

    K. Green, None

    B. L. Coleman, None

    J. Powis, None

    D. Richardson, None

    K. Katz, None

    B. Borgundvaag, None

    T. Smith-Gorvie, None

    J. C. Kwong, None

    S. Bondy, None

    A. Mcgeer, GSK: Grant Investigator and Scientific Advisor, Research grant
    Sanofi Pasteur: Grant Investigator and Scientific Advisor, Research support

    Findings in the abstracts are embargoed until 12:01 a.m. EDT, Oct. 8th with the exception of research findings presented at the IDWeek press conferences.

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