Association between intrahospital transfers and hospital-acquired infection among elderly patients: A retrospective case-control study in one urban UK hospital trust

Background Intrahospital transfers have become more common as hospital staff balance patient needs with bed availability. However, this may leave patients more vulnerable to potential pathogen transmission routes via increased exposure to contaminated surfaces and contacts with individuals. Objective This study aimed to quantify the association between the number of intrahospital transfers undergone during a hospital spell and the development of a hospital-acquired infection (HAI). Methods A retrospective case-control study was conducted using data extracted from electronic health records and microbiology cultures of non-elective, medical admissions to a large urban hospital trust comprising 3 hospital sites between 2016 and 2018 ( n =24,239). As elderly patients comprise a large proportion of hospital users and are a high-risk population for HAIs, the analysis focused on those over 65-years old. Logistic regression was conducted to obtain the odds ratio (OR) for developing a HAI as a function of intrahospital transfers until onset of HAI for cases, or hospital discharge for controls, while controlling for age, gender, time-at-risk, Elixhauser comorbidities, hospital site of admission, dominant treatment function code, intensive care admission, total number of procedures, and discharge destination. Results Of the 24,239 spells, 2879 cases were included in the analysis. 72.2% of spells contained at least one intrahospital transfer. On multivariable analysis, each additional intrahospital transfer increased the odds of acquiring a HAI by 9% (OR 1.09; 95%CI 1.05 to 1.13). Conclusion Intrahospital transfers are associated with increased odds of developing a HAI. Strategies for minimising intrahospital transfers should be considered, and further research is needed to identify unnecessary transfers. Their reduction may diminish spread of contagious pathogens in the hospital environment.