Using competing risk and multistate model to estimate the impact of nosocomial infection on length of stay and mortality in burn patients in Southeast China

OBJECTIVE: Due to the defects in skin barrier function and immune response, burn patients who survive the acute phase of a burn injury are at a high risk of nosocomial infection (NI). The aim of this study is to evaluate the impacts of NI on length of stay (LOS) and hospital mortality in burn patients using a multistate model. DESIGN AND SETTING: A retrospective observational study was conducted in burn unit and intensive care unit in the First Affiliated Hospital of Wenzhou Medical University, Wenzhou, China. PARTICIPANTS: Data were obtained from 1143 records of patients admitted with burn between 1 January 2013 and 31 December 2016. METHODS: Risk factors for NIs were determined by binary logistic regression. The extended Cox model with time-varying covariates was used to determine the impact of NIs on hospital mortality, and cumulative incidence functions were calculated. Multiple linear regression analysis was applied to detect the variables associated with LOS. Using a multistate model, the extra LOS due to NI were determined. RESULTS: 15.8% of total burn patients suffered from NIs and incidence density of NIs was 9.6 per 1000 patient-days. NIs significantly increased the rate of death (HR 4.266, 95% CI 2.218 to 8.208, p=0.000). The cumulative probability of death for patients with NI was greater that for those without NI. The extra LOS due to NIs was 17.68 days (95% CI 11.31 to 24.05). CONCLUSIONS: Using appropriate statistical methods, the present study further illustrated that NIs were associated with the increased cumulative incidence of burn death and increased LOS in burn patients.