Radiological findings and correlation to clinical outcome in patients admitted due to influenza A (H1N1) infection

OBJECTIVES : To examine whether radiological and clinical variables of patients hospitalized with H1N1 influenza infection are associated with disease severity and help predicting prognosis. MATERIAL: A retrospective observational study, which included patients hospitalized for influenza AH1N1 confirmed infection during 2009-2010, 2010-2011.Multivariate analysis was performed looking for variables that predicted the primary outcome (ICU admission and / or death during hospitalization), showing the results of the confidence intervals at 95% for the OR. RESULTS : during the study periods 98 patients with confirmed Influenza AH1N1 infection were admitted to our hospital, 16.3% requiring ICU admission and total hospital mortality of 6.1%. Regarding the radiological characteristics at admission, 26.8% had a normal study, 38.8% bilateral infiltrates and 24.5% unilateral infiltrates. Patients who met the primary outcome differed by a higher percentage of males, pregnant, bilateral infiltrates on admission, worse SpO2 and a higher percentage of complicated disease. Multivariate analysis showed that the only variable that was significantly associated with the outcome was the SpO2 (p< 0,001), with a trend toward statistical significance for unilateral infiltrates.Although fewer patients were diagnosed in the period 2010-2011, their condition was more serious according to SpO2, and up to 44% required admission to the ICU, compared with only 5.6% in the patients diagnosed during 2010-2011. CONCLUSIONS : Influenza AH1N1 infection associated with ICU admission and/ or mortality during hospital admission may be determined by the degree of respiratory failure present at the ED.