Children Coinfected With Complicated Pneumonia and Influenza Have Worse Outcomes

From Medscape Medical News

Laurie Barclay, MD

February 14, 2011 — Children coinfected with complicated pneumonia and influenza have worse outcomes than those without documented influenza coinfection, according to the results of a retrospective cohort study reported online February 7 in the Archives of Pediatrics & Adolescent Medicine.

"[A]lthough the association between complicated bacterial pneumonia and influenza has been recognized, no studies to our knowledge have specifically examined the impact of influenza coinfection on disease severity for children with complicated bacterial pneumonia, a group potentially at extremely high risk for poor outcomes," write Derek J. Williams, MD, MPH, from the Division of Pediatric Hospital Medicine, Vanderbilt University School of Medicine and the Monroe Carell Jr. Children's Hospital at Vanderbilt in Nashville, Tennessee, and colleagues.

"Thus, this study sought to address this issue through the use of a large retrospective cohort of children with complicated pneumonia from 40 children's hospitals nationwide. The primary objective was to determine whether influenza coinfection is independently associated with worse clinical outcomes."

The study cohort consisted of children with complicated pneumonia requiring a pleural drainage. These children were discharged between January 1, 2004, and June 30, 2009, from 40 children's hospitals contributing data to the Pediatric Health Information System. The chief exposure studied was influenza coinfection, and the primary study endpoints were intensive care unit (ICU) admission, use of mechanical ventilation, use of vasoactive infusions, use of blood product transfusions, in-hospital mortality, readmission within 14 days of hospital discharge, hospital length of stay, and hospitalization costs.

Of 9680 children with complicated pneumonia, 3382 underwent pleural fluid drainage, and 105 (3.1%) of these patients undergoing pleural drainage had influenza coinfection. A bacterial pathogen was identified in more than one third of cases (35.5%; n = 1201). In children with influenza coinfection, Staphylococcus aureus was the most frequently identified bacteria (in 22.9% of cases), whereas in children without coinfection, Streptococcus pneumoniae was most common (20.0% of cases).

Children coinfected with influenza were more likely than those without coinfection to have ICU admission; receipt of mechanical ventilation, vasoactive infusions, and blood product transfusions; higher costs; and a longer hospital stay. Although children coinfected with influenza were less likely to require readmission, they exhibited a trend toward higher odds of mortality. In the subgroups of children with S aureus and with no specified bacteria, coinfected children still had worse outcomes.

"Influenza coinfection occurred in 3.1% of children with complicated pneumonia," the study authors write. "Clinical outcomes for children with complicated pneumonia and influenza coinfection were more severe than for children without documented influenza coinfection."

Limitations of this study include lack of reliability of discharge diagnosis codes for specific diseases or pathogens, possible misclassification of bacterial pathogens, and possible failure to identify some patients with influenza coinfection because of miscoding or absence of influenza testing.

"These findings are consistent with other studies performed on a smaller scale and serve to alert the clinician that viral testing is an important consideration in children with complicated pneumonia, particularly in those with a more severe clinical course," the study authors conclude. "Moreover, our findings underscore the importance of routine influenza vaccination for children."

Arch Pediatr Adolesc Med. Published online February 7, 2011. Abstract