790 infection control & hospital epidemiology july 2018, vol. 39, no. 7
and/or DVT. Infectious adverse events included hospital onset Clostridium difficile infection (CDI), catheter-associated urin- ary tract infection (CAUTI), central-line–associated blood- stream infection (CLABSI), postoperative sepsis, surgical site infection (SSI), and ventilator-associated pneumonia (VAP). Table 1 describes the source of each adverse event. If data could be collected from >1 source, the data were aggregated, and duplicate events were removed. Adverse events were defined and collected according to the standardized definitions provided by each agency prior to the study for regulatory reporting purposes by hospital employees. The date used for inclusion in either the preintervention or postintervention period was the exact event date entered into the database, or if not available, the date of discharge. There were no major changes in collection methodology or reporting during the study period, except CAUTI which excluded yeast and colony counts less than 100,000 in 2015. This study was deemed exempt by the UCLA Institutional
Review Board as nonhuman subject research given that the data were collected for quality improvement purposes prior to the study. Each adverse event was associated with an isolation type,
either “MRSA and/or VRE,”“other isolation” (ie, multidrug- resistant Acinetobacter, carbapenem-resistant Enterobacter- iaceae, aminoglycoside-resistant Pseudomonas, and CDI), “combination” (ie, other isolation + MRSA/VRE), and “no isolation.” Additional isolation statuses, including droplet, airborne, or syndromic indications for isolation, were not evaluated in this study. The data regarding isolation status were collected from the electronic health record. In the post- intervention period, patients were not isolated for MRSA/ VRE, so they did not have an electronic isolation alert. Instead, investigators applied previous criteria for MRSA/VRE isolation (history of MRSA/VRE alerts in the electronic
table 2. Demographics of Patients With an Adverse Event Infectious
Adverse Events Variable
Age, y (SD) Male, %
Length of stay, d (SD)
Insurance, % Medicare MediCal ICU
Transplant
Hospital primary team, % Medicine Surgery Other
CCI (SD)
Preintervention (n=523)
52 (±22) 45
53 (±100) 38
20 43 20
29 60 11
2.8 (±2.0)
Postintervention (n=505)
54 (±21) 49
44 (±83) 35
19 38 20
31 58 10
3.0 (±2.1)
health record in the previous 5 years, positive MRSA/ VRE screening culture or clinical culture in the previous 2 years) to determine who would have previously qualified for isolation. A chart review was performed to collect demo- graphic and hospitalization-specific data for patients with an adverse event.
Statistical Analysis
Patient characteristics for those who experienced infectious or noninfectious adverse events were summarized preinterven- tion and postintervention (ie, before and after CP dis- continuation) using means for continuous variables and frequencies (%) for categorical variables (Table 2). We assessed the effect of a policy change in which CP was discontinued on adverse events using 2 approaches. First, we tested for overall differences in adverse event rates pre- intervention and postintervention using Poisson regression models by including only a preintervention and post- intervention predictor variable (Tables 3 and 4). We then ran longitudinal Poisson models considering monthly trends in adverse event incidence to test for immediate effects of the intervention as well as compute slope differences pre- intervention and postintervention. This analysis was carried out using interrupted time series analysis (segmented regres- sion analysis) as described by Wagner et al.40 Specifically, we used Poisson mixed-effects models with the outcome as the adverse event of interest and predictor terms for the baseline trend, level change after the intervention, trend change after intervention, and a patient random effect. The rates are reported per 1,000 admissions unless otherwise noted. Statis- tical summaries (incidence rate ratios, 95% confidence inter- vals, P values) and figures from these models are presented in Figures 1 and 2 and Tables 3 and 4.
Noninfectious Adverse Events
Preintervention (n=312)
56 (±20) 63
39 (±52) 45
25 40 27
13 82 4
2.8 (±1.9) NOTE. SD, standard deviation; MediCal, California Medicaid; CCI, Charlson comorbidity index.
Postintervention (n=260)
57 (±18) 59
39 (±71) 44
25 45 20
12 83 5
2.9 (±2.1)
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