Antimicrobial Utilization for Asymptomatic Bacteriuria and Culture-Negative Pyuria

Background:  Asymptomatic bacteriuria and candidiuria (ABC) are common and usually require no antimicrobial therapy.  Similarly, culture-negatve pyuria (CNP) is nonspecific and also rarely indicates underlying urinary tract infection (UTI).  Antimicrobial prescribing practices often do not conform to established evidence-based guidelines and lead to excessive antimicrobial use, risking increased antimicrobial resistance and adverse events.

Objective: We conducted a retrospective review of electronic medical records to characterize antimicrobial prescribing practices for ABC and CNP.

Methods: Medical records of inpatients at the acute care teaching hospital of the Boston Veteran’s Affairs Health Care System were reviewed. Patients with abnormal urinalyses and urine cultures with any growth were randomly identified from the laboratory database.  Abnormal urinalyses included those with pyuria, leukocyte esterase or nitrite positivity.  Patient demographics and clinical characteristics including co-morbidities and symptoms suggestive of UTI were collected. Cases were categorized as UTI, ABC, or CNP. The total number of antimicrobial days attributed to the abnormal urinary laboratory studies was determined. 

Results: 77 charts met inclusion criteria.  The inpatients included 3 women and 74 men with an average age of 72 years.  The most-common co-morbidies were diabetes mellitus (27%), malignancy (26%), spinal cord injury (25%), and benign prostatic hypertrophy or alpha-blocker therapy (23%).  Indwelling urinary catheters were present in 42% of patients.  The most commonly recorded symptoms were fever (25%), systemic inflammatory response syndrome physiology (17%), altered mental status (17%), dysuria (3.9%), autonomic dysreflexia (2.6%), urgency (1.3%) and frequency (1.3%).  11 cases were categorized as consistent with a UTI.  Each UTI was treated appropriately and received an average of 10.4 antimicrobial days, excluding one case of an infected urinoma that received a longer course. Among the 66 remaining cases, 4 were categorized as CNP and 62 as ABC.  None of the CNP cases resulted in antimicrobial therapy.  27% of ASB cases received antimicrobials for an average of 5.2 days, for a total of 88 patient days of excess antimicrobial exposure.

Conclusions:  Abnormal urinalyses and urine cultures with any growth are infrequently associated with clinical signs or symptoms compatible with a UTI, even among this veteran population with significant co-morbidities. ABC resulted in inappropriate antimicrobial exposure in over a quarter of our study cohort.  CNP was less common in this cohort but was not associated with inappropriate antimicrobial exposure.  Educational interventions for improving antimicrobial use for UTI should focus on evidence-based criteria for avoiding treatment of ABC except in very specific circumstances.