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Influenza surveillance case definitions miss a substantial proportion of older adults hospitalized with laboratory-confirmed influenza: A report from the Canadian Immunization Research Network (CIRN) Serious Outcomes Surveillance (SOS) Network

Published online by Cambridge University Press:  09 March 2020

Melissa K. Andrew Open the ORCID record for Melissa K. Andrew [Opens in a new window] ,
Janet E. McElhaney ,
Allison A. McGeer ,
Todd F. Hatchette ,
Jason Leblanc ,
Duncan Webster ,
William Bowie ,
Andre Poirier ,
Michaela K. Nichols  and
Shelly A. McNeil
...Show all authors
Melissa K. Andrew*
Affiliation:
Department of Medicine (Geriatrics), Dalhousie University, Halifax, Nova Scotia, Canada Canadian Center for Vaccinology, IWK Health Centre and Nova Scotia Health Authority, Dalhousie University, Halifax, Nova Scotia, Canada
Janet E. McElhaney
Affiliation:
Health Sciences North Research Institute, Sudbury, Ontario, Canada
Allison A. McGeer
Affiliation:
Mount Sinai Hospital, Toronto, Ontario, Canada
Todd F. Hatchette
Affiliation:
Department of Medicine (Geriatrics), Dalhousie University, Halifax, Nova Scotia, Canada Canadian Center for Vaccinology, IWK Health Centre and Nova Scotia Health Authority, Dalhousie University, Halifax, Nova Scotia, Canada
Jason Leblanc
Affiliation:
Canadian Center for Vaccinology, IWK Health Centre and Nova Scotia Health Authority, Dalhousie University, Halifax, Nova Scotia, Canada Department of Pathology, Dalhousie University, Halifax, Nova Scotia, Canada
Duncan Webster
Affiliation:
Saint John Regional Hospital, Dalhousie University, Saint John, New Brunswick, Canada
William Bowie
Affiliation:
Division of Infectious Diseases, University of British Columbia, Vancouver, British Columbia, Canada
Andre Poirier
Affiliation:
Centre Intégré Universitaire de santé et services sociaux, Quebec, Quebec, Canada
Michaela K. Nichols
Affiliation:
Canadian Center for Vaccinology, IWK Health Centre and Nova Scotia Health Authority, Dalhousie University, Halifax, Nova Scotia, Canada
Shelly A. McNeil
Affiliation:
Department of Medicine (Geriatrics), Dalhousie University, Halifax, Nova Scotia, Canada Canadian Center for Vaccinology, IWK Health Centre and Nova Scotia Health Authority, Dalhousie University, Halifax, Nova Scotia, Canada
*
Author for correspondence: Melissa K. Andrew, MD, PhD, E-mail: mandrew@dal.ca
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Abstract

Objective:

Older adults often have atypical presentation of illness and are particularly vulnerable to influenza and its sequelae, making the validity of influenza case definitions particularly relevant. We sought to assess the performance of influenza-like illness (ILI) and severe acute respiratory illness (SARI) criteria in hospitalized older adults.

Design:

Prospective cohort study.

Setting:

The Serious Outcomes Surveillance Network of the Canadian Immunization Research Network undertakes active surveillance for influenza among hospitalized adults.

Methods:

Data were pooled from 3 influenza seasons: 2011/12, 2012/13, and 2013/14. The ILI and SARI criteria were defined clinically, and influenza was laboratory confirmed. Frailty was measured using a validated frailty index.

Results:

Of 11,379 adult inpatients (7,254 aged ≥65 years), 4,942 (2,948 aged ≥65 years) had laboratory-confirmed influenza. Their median age was 72 years (interquartile range [IQR], 58–82) and 52.6% were women. The sensitivity of ILI criteria was 51.1% (95% confidence interval [CI], 49.6–52.6) for younger adults versus 44.6% (95% CI, 43.6–45.8) for older adults. SARI criteria were met by 64.1% (95% CI, 62.7–65.6) of younger adults versus 57.1% (95% CI, 55.9–58.2) of older adults with laboratory-confirmed influenza. Patients with influenza who were prefrail or frail were less likely to meet ILI and SARI case definitions.

Conclusions:

A substantial proportion of older adults, particularly those who are frail, are missed by standard ILI and SARI case definitions. Surveillance using these case definitions is biased toward identifying younger cases, and does not capture the true burden of influenza. Because of the substantial fraction of cases missed, surveillance definitions should not be used to guide diagnosis and clinical management of influenza.

Information

Type
Original Article
Information
Infection Control & Hospital Epidemiology , Volume 41 , Issue 5 , May 2020 , pp. 499 - 504
Copyright
© 2020 by The Society for Healthcare Epidemiology of America. All rights reserved

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Footnotes

PREVIOUS PRESENTATION: An earlier version of this work was presented as an oral abstract at the Canadian Immunization Conference, on December 6, 2018, in Ottawa, Ontario, Canada.

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