Fewer urine cultures — series of changes add up

As for where urine tests appear in the CPOE system, Dr. Warren says, “Subtle changes can have pretty big effects.”

An interdisciplinary team looked specifically at order sets for the emergency department. “We moved ‘urine culture’ off of their frequently ordered tests” in the ED electronic order set, “and we kept ‘urinalysis with reflex to microscopy,’” he says. “They could still order a reflex urine culture or a urine culture by itself, but they were two to three clicks away in the computer.”

This intervention in 2015 reduced the daily culture rate per 1,000 ED visits by 46.6 percent, but urinalysis, microscopy, and catheterized urine culture rates were unchanged (Munigala S, et al. BMJ Qual Saf. 2018;27[8]:587–592).

“One of the concerns was, were we inappropriately missing people who should have gotten a urine culture?” Dr. Warren says. “So one of the things we looked at was, with people who had gotten admitted to the hospital, what proportion of those patients had a urine culture within 24 hours of admission, suggesting that the primary team felt that the urine culture was missed. And we saw no increase in that percent of patients over time.”

A standalone urine culture must remain orderable for those who need it, Dr. Yarbrough says, such as pregnant women and perhaps urology patients, “but you need to make it harder to find for places like the emergency department.”

Another lesson learned: “If you’re a hospital that has immunosuppressed patients, be sure that the reflex algorithms for this patient population, such as transplant or oncology patients, are not restricted to a urine reflex algorithm that relies on pyuria or white blood cells as its main criteria,” Dr. Yarbrough says. “These patients are often neutropenic, so having white blood cells as a reflex parameter is not useful for that patient population.”

To address this, a second reflex algorithm was created called the UA reflex algorithm for neutropenic patients. Says Dr. Warren: “We allowed—if they had a positive blood, protein, leukocyte esterase, nitrite—if any of those were present, then it would potentially reflex to microscopy and urine culture. The concern with those patients was that because they’re neutropenic, they may not be able to mount a leukocyte response, and so the leukocyte esterase may be negative. So we wanted to increase the sensitivity in that patient population because we felt they were more at risk, and we realized we may have to trade off the specificity.”

Even today the laboratory is still working to refine its clinical decision support, with the aim of optimizing how urine culture results are displayed in the EMR.

“Although the algorithm is working to help optimize utilization of our urine cultures, many patients in our hospital do continue to have inappropriate repeat urine cultures ordered,” Dr. Yarbrough says. “This often occurs after collection of the initial sample in the emergency department. Then the patient gets admitted, and a repeat urine culture is ordered on the floor.”

Dr. Warren and colleagues conducted a retrospective study of adult inpatients who had one or more urine cultures performed during their hospitalization between January 2015 and February 2018 and found that 7.3 percent of urine cultures were repeated within 48 hours of the index urine culture. Of those, 54.4 percent were found to be inappropriate, defined as a culture performed after a negative index culture or a repeat urine culture on a specimen obtained from the same urinary catheter (Foong KS, et al. J Clin Microbiol. 2019;57[10]:e00910–e00919).

“Among inpatients with a negative index urine culture,” the authors of the study wrote, “the diagnostic gain of an inappropriate urine culture repeated within 48 hours for detecting bacteriuria was only 4.7 percent.”

A more than fivefold increased risk for having inappropriate inpatient repeat cultures performed within 48 hours after the index culture was found when the initial culture was performed with a sample obtained in the ED.

Says Dr. Warren, “We noticed there was a large proportion of hospitalized patients with a urine culture ordered, about 20 percent, that had duplicate urine cultures ordered, especially in the emergency department to inpatient transition.”

The study’s findings led to an alert added in recent months for duplicate urine culture testing, one they had planned to add at the start of this year but were unable to do so because of the pandemic.

The estimated laboratory charges for inappropriate repeat urine cultures were $16,800 over the study period, according to the authors.

New emerging technologies may hold promise for improved UTI diagnosis, but Dr. Yarbrough says more published studies are needed. So far, “not many of them are consistently reliable.”

“The real limitation is that current technologies, such as flow cytometry, for the detection of bacteria in urine do not provide all the necessary information,” she says. “For example, contaminated urine cultures may flag positive under the flow cytometry method. Also, you don’t get the identification of the organism or antimicrobial susceptibility information that would help you treat.”

What is needed are technologies that have a shorter assay time compared with culture, she says, ones “that are adaptable to point of care but that also discriminate uropathogens from contaminating organisms, or that are capable of measuring biomarkers of the host immune response to help determine the clinical relevance of bacteria in the urine.”

Amy Carpenter Aquino is CAP TODAY senior editor.