Influenza in hospitalised patients with malignancy: a propensity score matching analysis

BACKGROUND: Patients with malignancy are vulnerable to influenza viruses and are at high risk of developing serious complications. However, few studies have investigated the impact of influenza infection among hospitalised patients with malignancy. METHODS: Cancer-related hospitalisations were identified by using data from National Inpatient Sample in the USA between 2012 and 2014. We conducted a 1:1 propensity score matching analysis to compare the in-hospital outcomes between cancer patients with and without influenza. Multivariate logistic regression analyses were also performed to identify independent prognosis predictors of mortality. RESULTS: We identified 13 186 849 weighted cancer-related hospitalisations during the study period, and 47 850 of them (0.36%) had a concomitant diagnosis of influenza. After propensity score matching, cancer patients with concomitant influenza had a higher mortality (5.4% vs 4.2%; OR, 1.30; 95% CI, 1.13 to 1.49; p<0.001), longer length of stay (6.3 days vs 5.6 days; p<0.001) but lower costs (US$14 605.9 vs US$14 625.5; p<0.001) in hospital than those without influenza. In addition, cancer patients with influenza had a higher incidence of complications, including pneumonia (18.4% vs 13.2%; OR, 1.49; 95% CI, 1.37 to 1.62; p<0.001), neutropenia (7.1% vs 3.4%; OR, 2.18; 95% CI, 1.91 to 2.50; p<0.001), sepsis (19.5% vs 9.3%; OR, 2.36; 95% CI, 2.16 to 2.58; p<0.001), dehydration (14.8% vs 8.8%; OR, 1.80; 95% CI, 1.65 to 1.97; p<0.001) and acute kidney injury (19.9% vs 17.6%; OR, 1.16; 95% CI, 1.08 to 1.25; p<0.001) than those without influenza. Older age, no insurance, more comorbidities, lung cancer and haematological malignancy were independently associated with higher mortality. CONCLUSION: Influenza is associated with worse in-hospital clinical outcomes among hospitalised patients with malignancy. Annual influenza vaccination and early initiation of antiviral therapy are recommended in this high-risk population.