Q: Should I routinely obtain a urine culture from my asymptomatic inpatients? What if the urinalysis indicates the presence of both bacteria and white blood cells? What if my patient has a chronic indwelling catheter?
Context: Urinary tract infections (UTIs) are the most commonly encountered bacterial infections in the ambulatory, inpatient and long-term care settings. Asymptomatic bacteriuria—that is, presence of a ≥105 colony forming units/mL of bacteria in a urine sample without associated signs and symptoms of UTI—is even more common than UTI, with prevalence ranging from 1% in premenopausal women and diabetic men to up to 89-100% in patients who practice intermittent self-catheterization or have long-term indwelling catheters.
The Data: Between June 2013 and July 2014, the Johns Hopkins Hospital microbiology lab processed 1,383 urine cultures (1,142 clean catch and 241 catheterized samples). The cost of each urine culture is $11.00 - $40.00, resulting in $15,213 - $55,320 spent on urine cultures in the previous year.
Of the 1,383 specimens evaluated, 955 (69%) were either negative or were contaminated by urogenital flora alone. Among clean catch specimens, cultures were positive for pathogenic species only 26% of the time, while 53% of cultures from catheterized patients grew a pathogen.
Conclusion: Data from the Johns Hopkins Hospital demonstrate only a quarter of clean catch urine cultures yield an actual pathogen that can be used to guide therapy. This likely indicates high levels of unnecessary urine cultures being sent. Processing unnecessary urine cultures leads to increases in direct hospital costs and likely leads to significant indirect costs associated with diverted work effort in the microbiology lab and increased length of hospital stays and antibiotic costs.
Guidelines: According to the Infectious Disease Society of America, urine cultures should only be obtained in asymptomatic patients with bacteriuria in the following clinical situations: pregnant women (at least once during pregnancy), men who will undergo transurethral prostrate resection and men or women who will undergo any urologic procedure involving mucosal bleeding.1
Pyuria, or white blood cells in the urinary tract, is a common finding in patients with asymptomatic bacteriuria, with rates ranging from 30% in young or pregnant women to 90-100% of institutionalized elderly adults, patients on dialysis and patient with long-term indwelling catheters.1
Urinalysis and urine culture should not be obtained in catheterized patients without signs and symptoms of UTI (apart from pregnant women).2 Pyuria and foul odor alone are not indications for urine culture or treatment in catheterized patients.
Urine cultures should not be used to diagnose urinary tract infections, and cultures should not be ordered to guide treatment of uncomplicated cystitis. Urine cultures are helpful in directing therapy in patients with pyelonephritis, cystitis that has failed empiric therapy, pregnancy, men with obstructive prostatic disorders and patients with chronic indwelling catheters and/or a history of multi-drug resistant urinary pathogens.3
The Bottom Line: Urine cultures should only be ordered in specific clinical contexts: when treating pyelonephritis, complicated UTIs that failed empiric therapy and patients with signs of UTI and chronic indwelling catheters or a history of multi-drug resistant pathogens causing UTIs. Among asymptomatic patients, culture should only be obtained from pregnant women and patients who will undergo a urological procedure in which mucosal bleeding is anticipated.
- Clin Infect Dis. 2005 Mar 1;40(5):643-54. PMID: 15714408
- Clin Infect Dis. 2010 Mar 1;50(5):625-63. PMID: 20175247
- Clin Infect Dis. 2011 Mar 1;52(5):e103-20. PMID: 21292654
Written for the High Value Care Committee by Alexander Billioux, MD, DPhil.