Urine Culture on Admission Impacts Antibiotic Use and Length of Stay: A Retrospective Cohort Study

OBJECTIVE. To examine the impact of urine culture testing on day 1 of admission on inpatient antibiotic use and hospital length of stay (LOS). DESIGN. We performed a retrospective cohort study using a national dataset from 2009 to 2014. SETTING. The study used data from 230 hospitals in the United States. PARTICIPANTS. Admissions for adults 18 years and older were included in this study. Hospitalizations were matched with coarsened exact matching by facility, patient age, gender, Medicare severity-diagnosis related group (MS-DRG), and 3 measures of disease severity. METHODS. A multilevel Poisson model and a multilevel linear regression model were used to determine the impact of an admission urine culture on inpatient antibiotic use and LOS.RESULTSMatching produced a cohort of 88,481 patients (n = 41,070 with a culture on day 1, n = 47,411 without a culture). A urine culture on admission led to an increase in days of inpatient antibiotic use (incidence rate ratio, 1.26; P < .001) and resulted in an additional 36,607 days of inpatient antibiotic treatment. Urine culture on admission resulted in a 2.1% increase in LOS (P = .004). The predicted difference in bed days of care between admissions with and without a urine culture resulted in 6,071 additional bed days of care. The impact of urine culture testing varied by admitting diagnosis. CONCLUSIONS. Patients with a urine culture sent on day 1 of hospital admission receive more days of antibiotics and have a longer hospital stay than patients who do not have a urine culture. Targeted interventions may reduce the potential harms associated with low-yield urine cultures on day 1.