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Predictors of pandemic influenza infection in adults presenting to two urban emergency departments, Toronto, 2009

Published online by Cambridge University Press:  11 May 2015

Todd C. Lee ,
Linda R. Taggart ,
Barbara Mater ,
Kevin Katz  and
Allison McGeer
Todd C. Lee*
Affiliation:
Division of Infectious Diseases, University of Toronto, Toronto, ON
Linda R. Taggart
Affiliation:
Division of Infectious Diseases, University of Toronto, Toronto, ON
Barbara Mater
Affiliation:
North York General Hospital, Toronto, ON
Kevin Katz
Affiliation:
Division of Infectious Diseases, University of Toronto, Toronto, ON North York General Hospital, Toronto, ON
Allison McGeer
Affiliation:
Division of Infectious Diseases, University of Toronto, Toronto, ON Department of Microbiology, Mount Sinai Hospital, Toronto, ON
*
600 University Avenue, Room 1485, Toronto, ON M5G 1X5; [email protected]

Abstract

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Objective:

Identifying features that differentiate patients with H1N1 influenza infection from those with other conditions may assist clinical decision making during waves of pandemic influenza activity.

Methods:

From April 27 to June 15, 2009, nasopharyngeal swabs were obtained from all adults presenting to two urban emergency departments (EDs) with illness including fever or respiratory symptoms. H1N1 infection was detected by reverse transcriptase–polymerase chain reaction. Chart review was performed to compare cases of H1N1 influenza (n = 117) to matched controls.

Results:

The median age of cases was 35 years versus 50 years for controls (p < .001). In those with pre-existing conditions, asthma was present in 31% of cases versus 14% of controls (OR 2.6, 95% CI 1.3–5.4). Cough (OR 7.8, 95% CI 3.2–19), fever (OR 3.0, 95% CI 1.7–5.4), headache (OR 2.0, 95% CI 1.2–3.2), and myalgias (OR 1.9, 95% CI 1.2–3.1) were significantly more common in H1N1 cases. The median white blood cell count was 5.7 × 109/mL versus 10.9 × 109/mL (p < .001). The combination of fever and cough had an OR of 5.3. Fever, cough, low white blood cell (WBC) count, and tachycardia had the highest OR at 11. The absence of both fever and cough had a negative predictive value of 99%, but this occurred in only 8% of controls.

Conclusion:

In patients presenting to the ED, the combination of fever, cough, tachycardia, and WBC count < 10 × 109/mL was suggestive of H1N1 influenza infection. However, clinical features could not reliably distinguish influenza from other acute respiratory illnesses in adult ED patients.

Keywords

diagnosisinfluenzasymptoms
Type
Original Research • Recherche originale
Information
Canadian Journal of Emergency Medicine , Volume 13 , Issue 1 , January 2011 , pp. 7 - 12
Copyright
Copyright © Canadian Association of Emergency Physicians 2011

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