Patients

This was a prospective, observational study carried out in the adult intensive care units (ICU) of Amiens University Hospital, France, between September 2009 and March 2016 in all patients in whom influenza A(H1N1)pdm09 virus infection was diagnosed during or 1-week prior to the ICU stay.

Diagnosis of influenza A(H1N1)pdm09 infection was based on the presence of influenza or influenza-like illness, pneumonia, bilateral pulmonary infiltrates, and a positive result on a real-time polymerase chain reaction (RT-PCR) tests for microbiological confirmation of H1N1 influenza.

Demographic and clinical data at admission and during the ICU stay were recorded from the medical files of each patient and collected in a database to evaluate variables potentially associated with in-hospital mortality. Data baselines were recorded at admission. Mechanical ventilation, extracorporeal membrane oxygenation (ECMO) requirements, and the use of vasopressor drugs were noted during ICU stay. To determine illness severity, SAPSII and SOFA scoring systems were applied to all patients within 24 h of ICU admission.

This study was approved by the Institutional Review Board for Human Subjects. Patients or relatives provided their informed consent. The serum MBL of an historical control group was used to compare the levels of survivors and non-survivors.