Antibiotic Stewardship vs. Diagnostic Stewardship for Reducing Unnecessary Antibiotics in Asymptomatic Bacteriuria

By Richard R. Watkins, MD, MS, FACP, FIDSA, FISAC

Professor of Internal Medicine, Northeast Ohio Medical University, Rootstown, OH

SYNOPSIS: A statewide quality study compared antibiotic stewardship to diagnostic stewardship for hospitalized patients with asymptomatic bacteriuria. It found that reducing urine cultures decreased unnecessary antibiotic prescribing better than antibiotic stewardship.

SOURCE: Vaughn VM, Gupta A, Petty LA, et al. A statewide quality initiative to reduce unnecessary antibiotic treatment of asymptomatic bacteriuria. JAMA Intern Med 2023;183:933-941.

The treatment of asymptomatic bacteriuria (ASB) does not benefit most patients. Moreover, the overuse of antibiotics is the main driver for the spread of antibiotic resistance. Single-center studies have shown that both antibiotic and diagnostic stewardship can reduce unnecessary antibiotic use in ASB. Vaughn and colleagues sought to compare which of these two strategies is more effective.

The study was conducted over a three-year period and included 46 hospitals throughout Michigan. Eligibility criteria included having a positive urine culture and not receiving antibiotics for another infection during hospitalization. Patients were excluded who were admitted to intensive care, were pregnant, were immunocompromised, had a urine culture positive for Candida, had altered urinary anatomy, underwent a urologic procedure during hospitalization, or were receiving treatment for a urinary tract infection (UTI) at the time of admission. Patients were defined as having ASB if they had no signs or symptoms of a UTI based on national guidelines.

The primary outcome of the study was the overall improvement in ASB-related antibiotic use, which was estimated as the change in the percentage of patients treated with antibiotics who had ASB. This metric was used because it measures improvement that occurs both from diagnostic stewardship (i.e., more selective urine culturing) and antibiotic stewardship (i.e., not prescribing antibiotics for patients in whom ASB has been identified). The effect of diagnostic stewardship was estimated as the change in the percentage of patients with a positive urine culture who had ASB. The effect of antibiotic stewardship was estimated as the change in the percentage of patients with ASB who received antibiotics and antibiotic duration.

The study included 14,572 patients, and 28.4% (n = 4,134) had ASB (range across hospitals, 16.4% to 48.7%). Of all patients with ASB, 76.8% (n = 3,175) received antibiotic therapy (range across hospitals, 50.8% to 100%). In patients with ASB who received antibiotics, the median duration was six (range, four to eight) days. For diagnostic stewardship, the percentage of patients with a positive urine culture who had ASB decreased from 34.1% (95% confidence interval [CI], 31.0% to 37.3%) to 22.5% (95% CI, 19.7% to 25.6%) (adjusted odds ratio [aOR], 0.95 per quarter; 95% CI, 0.93-0.97; P < 0.001).

For antibiotic stewardship, the percentage of patients with ASB who were treated with antibiotics remained stable, from 82.0% (95% CI, 77.7% to 85.6%) to 76.3% (95% CI, 68.5% to 82.6%) (aOR, 0.97 per quarter; 95% CI, 0.94-1.01; P = 0.09). There was a minor decrease in the mean duration of antibiotic therapy for ASB, from 6.38 days (95% CI, 6.00-6.78 days) to 5.93 days (95% CI, 5.54-6.35 days) (adjusted incidence rate ratio, 0.99 per quarter; 95% CI, 0.99-1.00; P = 0.045).

COMMENTARY

This study showed a decrease in antibiotic prescribing through diagnostic stewardship, with antibiotic stewardship being relatively ineffective. These results are surprising given the strong emphasis on antibiotic stewardship over the last decade, especially in hospitals. Asking clinicians to not order a test is easier than asking them to not act on results, especially when the clinical scenario is equivocal (e.g., an elderly patient with a change in mental status). Indeed, decreasing urine cultures sent from the emergency department likely would have significant downstream effects. Operationalizing a diagnostic stewardship initiative focused on ASB and urine cultures is challenging but not insurmountable. Pragmatic interventions are needed and could include a call to the clinician from nursing, laboratory, or pharmacy personnel inquiring about the possibility of ASB. Another intervention could be to hide urine culture results from clinicians, which another study found reduced antibiotic prescribing for ASB from 48% to 12%.¹ Alerts in the electronic medical record could be designed that cue the clinician to consider ASB. It seems logical that multiple, simultaneous interventions would reduce unnecessary antibiotics for ASB more than single interventions alone. Further research is warranted to test this hypothesis.

The study had a few limitations worth consideration. First, there was no information on which diagnostic stewardship methods were the most effective. Second, the study was conducted at hospitals in a single Midwestern state, thus limiting its generalizability to other geographic locations and patient populations. Third, there was no control group of hospitalized patients in whom urine cultures were not collected yet who still may have received antibiotics. Finally, by relying on data collection from medical records, it is possible that documentation of symptoms increased over time, thus affecting the classification of UTI vs. ASB.

Diagnostic stewardship is an important tool for reducing unnecessary urine cultures in patients with ASB. Additional research is warranted to identify best practices that combine diagnostic stewardship with antibiotic stewardship so that antibiotics may be avoided for ASB.

REFERENCE

1. Spivak ES, Burk M, Zhang R, et al; Management of Urinary Tract Infections Medication Use Evaluation Group. Management of bacteriuria in Veterans Affairs hospitals. Clin Infect Dis 2017;65:910-917.