Get on the BUS
The researchers conducted a retrospective study across one academic medical center and four community hospitals in three states to assess the feasibility of using five categories of UTI diagnosis: The three existing ones plus LUTS/other urologic symptoms (OUS) and bacteriuria of unclear significance (BUS). These additional categories arose out of an hour-long discussion with a focus group of experts across several disciplines.
The analysis covered the charts of 3392 randomly selected encounters out of 220,531 total inpatient or emergency department encounters between January 2017 and December 2019 in which adults received a urinalysis and urine culture order within the same 24-hour period. The patients’ median age was 67 years, over half (59.6%) were women, and nearly a quarter (24.2%) had an underlying immunocompromising condition.
Most of the cultures were obtained from inpatients. Nearly a third (30.6%) were negative for culture, while 42.1% grew at least 100,000 CFU/mL of bacteria and 17% grew mixed flora.
Based on current criteria, 21.3% of the patients had a UTI, 20.8% had ASB, and 47.6% had no UTI. The remaining 10.3% had culture growth under 100,000 CFU/mL and, therefore, did not fit in any of these categories, “as there is no consistent guidance on whether to classify them as no UTI or ASB or contamination,” the authors wrote.
When the researchers applied the new criteria, more than half of the cases of ASB (68%) were reclassified as BUS, and 28.9% of the no-UTI cases were reclassified as LUTS/OUS.
In a sensitivity analysis that examined samples with bacteriuria below the 100,000 CFU/mL threshold, nearly half the unclassified cases (43.3%) were reassigned as a UTI, increasing the proportion of patients with a diagnosed UTI from 21.3% to 25.8% of the total population. Of the remaining patients who had originally been unclassified, 14.2% were newly defined as ASB, and 42.5% became BUS.
Dr. Abraham said the addition of the BUS and LUTS/OUS categories has the potential to improve and individualize patient care. Clinicians can consider nonantibiotic therapies for the patients who had LUTS/OUS while they look into possible causes, while the BUS cases enable frontline clinicians and antibiotic stewardship teams to “meet in the middle” by monitoring those patients more closely in case symptoms worsen, she said.
The authors highlighted three key takeaways from their study, starting with the fact that nearly two thirds of patients who underwent testing for a UTI did not have signs or symptoms localized to the urinary tract — the ones reclassified as BUS.
“Hence, reclassifying patients as BUS may provide an opportunity to acknowledge diagnostic uncertainty and need for additional monitoring than ASB patients so as to promote a nuanced and patient-centered approach to diagnosis and management,” the authors wrote.
Second, a third of patients initially classified as not having a UTI were reclassified into the new LUTS/OUS category because of their symptoms, such as a poor or intermittent stream, dribbling, hesitancy, frequency, urge incontinence, and nocturia. These patients would need further workup to determine the best approach to management.
Finally, the sensitivity analysis “suggested that lowering the bacterial threshold in some symptomatic patients may capture additional patients with UTI whose symptoms may be dismissed due to concern for contamination or attributed to LUTS rather than infection.” Given that the 100,000 CFU/mL threshold is based on a single study in 1956, the authors suggested more research may help define better CFU thresholds to improve clinical care.
Dr. Berookhim said the study authors took a reasonable and thorough approach in how they tried to consider the best way to update the current diagnostic classification schema.
“I think using this as a jumping off point to look deeper is worthwhile,” such as conducting randomized controlled trials to assess the use of new categories, he said. “Getting more granular than this, I think, would just muddy the waters and make it more difficult to make clinical decisions.”
The research was funded by the National Institute of Diabetes and Digestive and Kidney Diseases. Dr. Advani reported consulting fees from Locus Biosciences, Sysmex America, GlaxoSmithKline, and bioMérieux. Dr. Abraham and Dr. Berookhim reported no relevant financial conflicts of interest.
A version of this article appeared on Medscape.com.