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Interpretation of Urine Cultures: Downstream Implications

Posted on 03/18/15

Infection_Prevention_and_Antimicrobial_Stewardship_–_A_Natural_FitThe release of the CDC’s 2013 HAI Progress Report delivered a disappointing message about catheter-associated urinary tract infection (CAUTI) rates for patients in acute care hospitals: a 6% increase between 2009 and 2013. Among the key reduction strategies outlined by the Department of Health and Human Services (HHS) to address this increase is the implementation and improvement of antimicrobial stewardship.

An often cited concern about the reported rates of CAUTI is that the data is based on the NHSN surveillance definition, which includes the criteria of a positive urine culture associated with clinical signs and symptoms. Frequently, the non-specific symptom of fever ( >38o C ) or hypothermia ( <38o C ) in a patient leads to the ordering of cultures by the physician. If the urine culture is positive, the symptomatic UTI definition is met and must be reported to NHSN, even if the physician determines that the fever is clinically due to another recognized cause. A positive urine culture in the absence of signs and symptoms is labeled asymptomatic bacteriuria (ASB). With the current transparency of HAI data and potential reimbursement penalties, many healthcare organizations are revisiting guideline-based indications for urine culturing.

More important than the potential overestimation of CAUTI rates is the knowledge that treatment of UTI is a large contributor to inpatient antimicrobial use. A recent study published by Hartley and colleagues1 evaluated the indications for urine culturing, the appropriateness of antimicrobial use and rationale for the inappropriate treatment of ASB.

A review of 153 patient records found that more than 60% of the positive urine cultures represented ASB and treatment of these patients resulted in 435 days of unnecessary antimicrobial use. Of particular note is that the antimicrobials ordered for treatment of ASB were newly initiated and the mean duration of treatment was consistent with that used for a complicated infection (7.4 days). It was determined that 51% of the urine cultures were ordered without guideline-based indications or as part of a work-up for fever alone without other specific UTI signs and symptoms (for example, costovertebral angle tenderness or pain). Drivers of antimicrobial overuse included fever with an alternative source, altered mental status and leukocytosis. The authors recommend a second level of assessment after providers have initiated treatment for UTI to include a review of culture results, consideration of competing diagnoses that triggered the culturing and re-evaluation of the indications for antimicrobial therapy.

The implementation of guideline-based urine culturing protocols should be considered as a critical component for both the infection prevention and antimicrobial stewardship programs of a healthcare organization. These protocols may contribute to improved accuracy of data reporting and reduce the unnecessary use of antimicrobials.    

References

1 Hartley S, Valley S, Kuhn L, Washer L, Gandhi T, Meddings J, et al. Overtreatment of Asymptomatic Bacteriuria: Identifying Targets for Improvement. Infect Control Hosp Epidemiology Published online: 05 January 2015. Accessed March 17, 2015.

Topics: Infection Prevention

About the Author

Joan N. Hebden, RN, MS, CIC served as the Director of Infection Prevention and Control for 28 years at the University of Maryland Medical Center, Baltimore, MD. Her clinical background includes general medicine, oncology, and cardiothoracic intensive care. She has presented at national epidemiology conferences, participated in research regarding the transmission of multi-drug resistant bacteria, contributed chapters on infection control to nursing resource textbooks, and published in medical and infection control journals. Joan received her Bachelor of Science degree in nursing and a Master of Science degree in nursing education and trauma/critical care from the University of Maryland School of Nursing. She is certified in Infection Control & Epidemiology (CIC). Joan is an active member of SHEA and APIC and is currently on the Editorial Board of the American Journal of Infection Control (AJIC).