IMPORTANCE Although contact isolation has been widely recommended for multidrug-resistant organisms, contact isolation has raised some concerns that it may bring unintended patient harms.

OBJECTIVE To compare adverse events between a contact isolation group with vancomycin-resistant Enterococcus (VRE) and a matched comparison group using a relatively large data set from full electronic medical records (EMR) and propensity score-matching methods.

DESIGN, SETTING, AND PARTICIPANTS This retrospective, matched cohort study was conducted at Seoul National University Bundang Hospital (SNUBH) in Korea, a tertiary, university-affiliated hospital that has 1337 inpatient beds. Participants included a total of 98 529 hospitalized adult patients (aged ≥18 years) during 2015 to 2017.

EXPOSURES Contact isolation in a single or shared double room.

MAIN OUTCOMES AND MEASURES As adverse contact isolation-related outcomes, falls and pressure ulcers were included. All relevant EMR data were extracted from the SNUBH clinical data warehouse. Risk factors for adverse events were included in the propensity score model based on literature reviews, such as Braden scale score and Hendrich II fall risk score. A fine stratification and weighting (FSW) and a 1:10 nearest neighbor (NN) propensity score matching as a sensitivity analysis were adopted to compare adverse events between the 2 groups for the observation period from the study entry date and the exit date. Time-to-event analyses with a Cox proportional hazard model were conducted in December 2021.

RESULTS For comparison of outcomes in wards, 177 patients (mean [SD] age, 67.38 [14.12] years; 98 [55.4%] female) with VRE and 93 022 patients (mean [SD] age, 56.44 [16.88] years; 49 462 [53.2%] female) without VRE were included and no difference was found in basic characteristics from the FSW (VRE contact isolation [n = 172] vs comparison [n = 69 434]) as well as from the 1:10 NN (VRE contact isolation [n = 168] vs comparison [n = 1650]). Among 177 patients with VRE contact isolation, 8 pressure ulcers and 3 falls occurred during their hospital stays; incidence rates of adverse events were 2.5 and 0.9 per 1000 patient-days, respectively (pressure ulcer incidence rate from the FSW: 2.53 per 1000 patient-days [95% CI, 1.09-4.99 per 1000 patient-days]; pressure ulcer incidence rate from the 1:10 NN: 2.54 per 1000 patient-days [95% CI, 1.10-5.01 per 1000 patient-days]; fall incidence rate from the FSW: 0.87 per 1000 patient-days [95% CI, 0.18-2.54 per 1000 patient-days]; fall incidence rate from the 1:10 NN: 0.87 per 1000 patient-days [95% CI, 0.18-2.55 per 1000 patient-days]). The hazard ratios for adverse events showed no statistically significant differences for both groups: 1.42 (95% CI, 0.67-2.99) for pressure ulcer and 0.66 (95% CI, 0.20-2.13) for fall from the FSW.

CONCLUSIONS AND RELEVANCE In this cohort study, no association was found between the likelihood of adverse events and contact isolation using propensity score-matching methods and closely related covariates for adverse events.