A Hospital-Based Nonconcurrent Cohort Study on Factors Associated with in-Hospital Mortality in Patients with Laboratory Confirmed Influenza

BACKGROUND AND AIM: Influenza is a disease with varied clinical presentation and varied mortality reported in existing literature. The study aimed to determine the factors associated with mortality in patients hospitalized with influenza infection. MATERIALS AND METHODS: This was a 5-year nonconcurrent cohort study done in a tertiary care center in Southern India. Patients with laboratory confirmed influenza infection diagnosed between January 2013 and October 2018 were recruited into the study. RESULTS: A total of 130 patients were recruited. Diabetes (45.4%) and chronic obstructive pulmonary disease (COPD) (26.1%) were the most common comorbid illnesses. Thirty-one patients (23.8%) required admission to the intensive care unit (ICU) and 58 patients required ventilation (noninvasive/mechanical ventilation [MV] – 44.6%). Influenza A was the most common isolated strain (46.9%). Univariate analysis demonstrated that a high pneumonia severity index (P < 0.0001), CURB 65 > 2 (P < 0.0001), MV dependency (P < 0.0001), need for ICU stay (P < 0.0001), low PF ratio (P < 0.0001), COPD (P = 0.021), secondary bacterial pneumonia (P < 0.0001), acute respiratory distress syndrome (P = 0.0004), and acute kidney injury (P = 0.0006) were the significant factors associated with in-hospital mortality. Multivariate analysis demonstrated that new onset/worsening renal dysfunction was the only factor significantly associated with in-hospital mortality in patients admitted with influenza. CONCLUSIONS: Our study showed a mortality of 12.3% (n= 16) and new onset/worsening renal dysfunction was the only patient factor associated with mortality. Early recognition of complications and appropriate treatment may reduce mortality in patients admitted with severe influenza. We recommend influenza vaccination for at-risk populations to reduce severity and mortality.