Cutting Unneeded Urine Cultures a Good First Step to Less Antibiotic Use

WASHINGTON -- Michigan hospitals were able to cut down on unnecessary treatment of asymptomatic bacteriuria (ASB) thanks to better diagnostic stewardship, according to a study.

The percentage of patients with a positive urine culture who had ASB fell from 34.1% in the year 2017 to 22.5% in 2020 in a consortium of 46 hospitals. That meant less ASB patients were being tested, so they would not be treated with antibiotics for inappropriately diagnosed urinary tract infection (UTI), according to Valerie Vaughn, MD, MSc, of the Michigan Hospital Medicine Safety Consortium and a hospital medicine researcher at the University of Utah in Salt Lake City.

"Fewer tests in the wrong patients, means fewer antibiotics in the wrong patients. This leads to less antibiotic harm and less resistance," she explained in an interview with MedPage Today at this year's IDWeek meeting.

She noted that antibiotics do not improve outcomes in ASB, a common condition in hospitalized patients. Despite guidelines recommending against treatment, up to 80% of hospitalized ASB patients receive antibiotics, based on prior reports

Across the Michigan consortium of hospitals, there was no budging on antibiotic stewardship. The percentage of patients with ASB who were treated with antibiotics remained relatively stable, going from 82.0% to 76.3% during the study period. Moreover, the duration of antibiotics given dropped significantly but modestly, from a mean 6.38 days down to 5.93 days, Vaughn reported.

She noted that in a head-to-head comparison with antibiotic stewardship, diagnostic stewardship was a clear winner. "We prevented antibiotic treatment in 1,800 patients -- about 10,800 days of antibiotic use -- by stopping unneeded urine cultures," she said.

Nevertheless, she stressed that antibiotic stewardship and diagnostic stewardship are not necessarily separate interventions. Both can be incorporated in bundled interventions and activities such as education, audit, and feedback.

When implementing a program of diagnostic stewardship, Vaughn said it's important to ask, "Are you targeting cultures to the right patients? Out of all the positive, how many asymptomatic patients do you have, who should not have gotten a test to begin with? Did the right people get the right test?"

Participating Michigan hospitals had been equipped with data and given pay-for-performance incentives for reduced antimicrobial use.

The present study cohort included 14,572 patients with a positive urine culture, of whom 71.6% had a UTI and the rest ASB.

The 4,134 people with ASB were largely over 65 years of age, and women and white individuals each accounted for over 70% of the cohort.

Excluded from the analysis were people who were at hospitals that participated in less than half of the study period and those who had candida only, died, were transferred to intensive care, or were missing critical data. Also excluded were symptomatic patients who did not get antibiotics.

Trends in ASB treatment did not appear to differ by hospital characteristics.

However, limitations of the study included not having data on urine cultures over time, the lack of antibiotic use data for patients in whom urine cultures were avoided, and the reliance on a retrospective review of medical records.

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