Discussion

In this study, the implementation of a provider-selected indication requirement in the laboratory order interface for isolated urine-culture testing did not significantly decrease culture rates. Although we detected significant changes seen between intervention periods when comparing median culture rates, there was no significant difference in culture rates when analyzed using an interrupted time series analysis, which considers pre- and postintervention trends. ^{Reference Kontopantelis, Doran, Springate, Buchan and Reeves18} This finding supports the strengths of utilizing an analysis method that incorporates those trends when determining the potential impact of an intervention, compared to a before-and-after analysis which does not. The proportion of all urine test orders represented by isolated urine-culture orders did not differ significantly between study periods, and neither did the culture positivity. These findings reflecting the lack of change in ordering practices after the intervention.

Previous studies on the impact of indication specification requirements for isolated urine culture testing are limited. One prior multicenter study ^{Reference Watson, Trautner and Russo19} evaluated the effect of a new laboratory order interface that included a similar indication requirement in the implemented order set. This study reported a 40% reduction in culture rates after the intervention, although only 45% of orders placed after the intervention were appropriate based on chart review. ^{Reference Watson, Trautner and Russo19} Indication selection for testing remains underutilized in testing algorithms; a survey of acute-care hospitals in the Society for Healthcare Epidemiology Network (SRN) revealed that only 17% require specification of an order indication. ^{Reference Sullivan, Morgan and Leekha20} Although this study did not demonstrate successful reduction in testing as a result of this intervention, with specific improvements, namely removing the option to skip the selection of an indication, and possibly deleting the “other” category, this intervention has the potential to prompt appropriate testing.

Measuring appropriate use of urine testing is vital because it is one of the most frequently performed diagnostic tests in a hospital setting. One large national retrospective cohort study estimated that urine testing is performed in up to 47% of hospital admissions. ^{Reference Horstman, Spiegelman, Naik and Trautner21} Prior studies have estimated that 58%–68% of urine cultures sent in hospital settings are not for guideline-based indications, ^{Reference Leis, Gold, Daneman, Shojania and McGeer22,Reference Hartley, Valley and Kuhn23} suggesting that this testing is frequently misused. Smaller reviews have also found similar trends, with nearly 50% of testing ordered without a specified clinical indication and almost 30% for a nonspecific indication. ^{Reference Puig-Asensio, Hoff and Ince24} Our study had similar findings, with 67% of reviewed charts lacking a specific indication for isolated urine testing. Many of our study patients were tested for nonspecific findings, including broad evaluation for fever or increasing leukocytosis, and only 10% of patients had documented symptoms consistent with a urinary tract infection.

Overtreatment of asymptomatic bacteriuria represents a threat contributing to growing antimicrobial resistance. This is a frequent issue; retrospective studies having found that 32.8%–41% of patients with asymptomatic bacteriuria receive antibiotic therapy for a suspected UTI. ^{Reference Rotjanapan, Dosa and Thomas25,Reference Lin, Bhusal, Horwitz, Shelburne and Trautner26} Although we did find lower rates of antimicrobial prescription in asymptomatic patients than these prior studies, the ultimate goal is to eliminate treatment of asymptomatic bacteriuria altogether unless the patient meets one of the rare criteria to do so (eg, pregnant patients or those who are about to undergo invasive urologic surgery). Thus, much work remains to be done.

In our study, many providers did not select an indication for isolated urine-culture testing, despite being prompted by the laboratory order interface. The indication was left blank for 71.9% of the tests after the intervention began. Previous studies have found similar difficulties with indication selection, ^{Reference Watson, Trautner and Russo19} and the most commonly selected indication was the first indication on the list, even if not most appropriate, potentially reflecting a desire to expedite the ordering process rather than reading a longer list of indications. Although significant provider education was provided before, during, and after the intervention in our study by infectious disease physicians and infection prevention specialists, the nonsignificant results seen may reflect a need for a more strategic educational approach toward ordering providers.

Utilizing the results of the study, several next steps should be considered. First, an initial and simple intervention would be implementing a stricter algorithm that does not allow a lack of indication for ordering and eliminates the “other” indication category. Another intervention that may be considered given these results is further restriction of isolated urine testing by requiring approval by antimicrobial stewardship teams for order placement, which also allows continued provider education. A more drastic intervention that could be considered is the suppression of the reporting of urine cultures when ordered for noncatheterized patients with the option for ordering providers to request cultures be reported, which has been shown to have a strong impact on clinician behavior with a decrease in treatment of asymptomatic bacteriuria. ^{Reference Leis, Rebick and Daneman27}

This study had several limitations. It had a single-center design, and we did not have data on method of testing collection, such as whether the specimen was collected from a catheterized patient. Isolated culture testing is typically more common among patients with urinary catheters and patients in the intensive care units, ^{Reference Carlson, Munigala and Russo17} so these data would likely provide greater understanding of provider ordering practices and potential interventions. Another potential limitation is that the study period included the onset of the COVID-19 pandemic, which may have affected patient testing, potentially by decreasing testing because hospital capacity was limited and elective procedures were suspended. The sensitivity analysis performed did not show changes in the study results when the initial pandemic period was excluded; thus, the pandemic likely did not affect the intervention. We used >100,000 CFU as a criteria for positive culture. Although standard in the literature, ^{Reference Mody and Juthani-Mehta28} this parameter may have underestimated the number of true infections. Strengths of our study include that our dataset consisted of a large number of tests performed at an academic medical center with an accessible electronic ordering system, providing complete data. An additional strength was the utilization of the interrupted time series design; this design provided valuable insight into pre- and postintervention trends.

In conclusion, the addition of an indication specification requirement for isolated urine culture testing did not significantly decrease the isolated urine-culture rates at our institution. A review of the specified indications revealed that this testing was often inappropriately selected for patients. These findings highlight the need for more sophisticated diagnostic algorithms to guide providers to the most appropriate testing for their patients, with the goal of reducing treatment of asymptomatic bacteriuria. Although this study did not include a more in-depth evaluation into the driving factors causing overutilization of urine testing, the reasons are likely multifactorial including inappropriate beliefs about patient risks, practices of peers and mentors, and lack of knowledge. Gaining a better understanding of these implementation barriers is paramount because we can then design interventions to target these barriers, enabling the system to impart meaningful change.