VANCOUVER—Urine cultures ordered to evaluate for urinary tract infections (UTIs) in hospitalized patients with indwelling urinary catheters often are unnecessary, new data suggest.

“There needs to be clarification in how and when urine cultures should be ordered and how an electronic medical record might aid clinicians for this issue,” said lead investigator Michelle Hecker, MD, Assistant Professor of Medicine at Case Western Reserve Medical Center in Cleveland. “There needs to be a system approach to this problem. Although for the most part we as infectious diseases physicians encourage obtaining cultures before treating with antibiotics, obtaining cultures in the appropriate setting and appropriate way is what is most important.  Unnecessary urine cultures in many instances lead to unnecessary antibiotic treatment and unnecessary antibiotic therapy often leads to adverse drug events, superinfections and antibiotic resistance.  Our findings have significant implications for quality of care, patient safety, and certainly cost.”

Inpatients commonly have multiple urine samples submitted for culture. Urine cultures are often submitted because of the ease of obtaining the sample and the perceived low risk and low cost associated with obtaining the sample, Dr. Hecker said.

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In a retrospective study, Dr. Hecker and her colleagues examined the frequency of testing and reasons for UTI testing in 364 hospitalized patients with indwelling urinary catheters. The average duration of catheterization was 4.5 days. Of the 364 patients, 159 (44%) had one or more urine cultures performed (range 1-8). Urine cultures were deemed inappropriate if they were sent within 48 hours of another urine culture without a significant change in the patient’s status, if the patient had no symptoms or signs of infection, and if the only indication was foul smelling or cloudy urine. Urine cultures were also considered inappropriate if there was a clear alternative diagnosis for the signs or symptoms at the time the culture was sent or if the urinalysis was negative for leukocyte esterase and nitrate and had fewer than five white blood cells per high-power field.

Clinicians ordered a total of 229 urine cultures, of which 115 (50%) were deemed unnecessary, Dr. Hecker reported at the 48th Annual Meeting of the Infectious Diseases Society of America.

  Fifteen percent were considered unnecessary repeat cultures within 48 hours, 49% involved no symptoms or signs of infection, and 8% were performed because of smelly or cloudy urine alone. In 20% of cases, it was evident there was a clear alternative diagnosis, Dr. Hecker said. In addition, the researchers found that less than 1% of urine cultures were performed to see if a pathogen had cleared; 8% had a “normal urinalysis” with no leukocyte esterase, nitrite, or pyuria.

The 88 patients who had one or more inappropriate urine cultures had a mean age was 56 years (range 17-89 years) and 51% were female. Their mean length of hospital stay was 14 days.

“To my knowledge, this is the first study like this,” Dr. Hecker said. “Our findings suggest that there are number of areas where improvements could be made.”