Researchers Ponder When a Flu Diagnosis Should be Considered

There is a paucity of data about clinical characteristics that help identify patients at higher risk of influenza infection upon intensive care unit (ICU) admission. Stefan P. Kuster, of Mount Sinai Hospital in Toronto, and colleagues, aimed to identify predictors of influenza infection in patients admitted to ICUs during the 2007/08 and 2008/09 influenza seasons and the second wave of the 2009 H1N1 influenza pandemic and to identify populations with increased likelihood of seasonal and pandemic 2009 influenza (pH1N1) infection.

Six Toronto acute-care hospitals participated in active surveillance for laboratory-confirmed influenza requiring ICU admission during periods of influenza activity from 2007 to 2009. Nasopharyngeal (NP) swabs were obtained from patients presenting with acute respiratory or cardiac illness or febrile illness without clear non-respiratory etiology. Predictors of influenza were analyzed by multivariable logistic regression analysis and likelihoods of influenza in different populations calculated. Results 126 of 5,482 (2.3%) admissions were found to have influenza. Admission temperature [greater than or equal to]38degreesC (odds ratio (OR) 4.7 for pH1N1, 2.3 for seasonal) and admission diagnosis of pneumonia/respiratory infection (OR 7.3 for pH1N1; 4.2 for seasonal) were independent predictors for influenza.

During the peak weeks of influenza seasons, 17 percent of afebrile and 27 percent of febrile patients with pneumonia/respiratory infection had influenza. During the second wave of the 2009 pandemic, 26 percent of afebrile and 70 percent of febrile patients with pneumonia/respiratory infection had influenza.

The researchers say that their study findings may assist clinicians in decisions regarding optimal management of adult patients being admitted to ICUs during future influenza seasons. Influenza testing, empiric antiviral therapy and empiric infection control precautions should be considered in those patients who are admitted during influenza season with a diagnosis of pneumonia or respiratory infection and who are either febrile or admitted during weeks of peak influenza activity. Their research was published in Critical Care.

Reference: Kuster SP, Katz KC and Blair J, et al. When should a diagnosis of influenza be considered in adults requiring intensive care unit admission? Results from population-based active surveillance in Toronto. Critical Care 2011, 15:R182doi:10.1186/cc10331