Hospital Infection Rates Before and After Construction of a New Tertiary Care Facility: Importance of Risk Stratification

Background: Few studies have examined the impact of a move from one hospital to another with new construction on rates of nosocomial infection.  None has described changes in infection rates resulting from combining the staff of two older facilities, with differing patient demographics, staff, and clinical acuity, into one new facility. 

 

Objective: To describe the rates of blood stream infections (BSI), including central line associated BSI, surgical site infections: superficial, deep and organ-space (SSI), catheter-associated urinary tract infections (CAUTI), ventilator-associated pneumonia (VAP), and Clostridium difficile-associated diarrhea (CDAD) in the two years before and after the merging of Hospital A (a tertiary care, high-acuity teaching facility) and Hospital B (a non-teaching, community hospital) into one new facility, Hospital C (a tertiary care, teaching center). 

Methods: Four infection preventionists (IPs) identified cases of BSI, SSI, VAP, CAUTI, and CDAD infections using an electronic surveillance tool over the two years prior to the move (at Hospitals A and B: October 2005-October 2007), and the two years after (Hospital C: October 2007-October 2009). The same IPs examined all cases using similar case finding techniques except for SSI (with enhanced surveillance after move).  Cases were verified by IP review of the electronic medical record (EMR), and met CDC definitions.  Rates were calculated as infections per 1000 patient days.

Results: The demographics of Hospital C showed similar age and gender distribution to Hospitals A and B.  The proportion of patients with major or extreme severity of illness scores were highest at Hospital A (26%), lowest at Hospital B (15%) and intermediate at the merged facility, Hospital C (21%).   Infection rates were highest at Hospital A, lowest for Hospital B, and intermediate for Hospital C for BSI (A 2.0, 95% CI 1.8-2.2 vs. B 1.0, 0.7-1.2 vs. C 1.1, 0.9-1.2), UTI (A 4.4, 4.1-4.7 vs. B 1.7, 1.4-2.0 vs. C 3.1, 2.9-3.4), VAP (A 0.7, 0.6-0.8 vs. B 0.2, 0.1-0.3 vs. C 0.32, 0.2-0.4), and SSI (A 2.47, 2.3-2.7  vs. B 1.7, 1.4-1.9 vs. C 2.0, 1.8-2.2).   Rates of culturing in all forms were noted to be higher at Hospital C (33.8) than either A (26.2) or B (18.0) during the periods of study. 

Conclusions: With the merging of the two hospitals, the infection rates at the new facility were intermediate between those at the tertiary facility and the community facility, reflecting the intermediate severity of illness of the patients seen at the merged facility.  These results emphasize the need for risk stratification when comparing infection rates at various facilities.