Caught Up in CAUTIs: The Importance of Diagnostic Stewardship

Neil Gaffin, MD


August 01, 2022

"Diagnostic stewardship" refers to the appropriate use of laboratory testing to guide patient management, including treatment, to optimize clinical outcomes and limit the spread of antimicrobial resistance.[1] As an adjunct to existing antimicrobial stewardship programs, diagnostic stewardship for hospital-onset Clostridioides difficile infection (HO-CDI) has been shown to result in safe reductions in the nosocomial acquisition of this infection.[2,3,4] We need diagnostic stewardship for other hospital-acquired infections as well.

Urine cultures rank high on the list of tests that are often performed unnecessarily or inappropriately. They are commonly ordered during diagnostic workups for the myriad presentations that might have an infectious etiology. However, because the bladder is not sterile, interpreting the significance of bacterial growth even in the presence of pyuria can be problematic, particularly in the absence of focal genitourinary symptoms.[5] This applies to individuals with and without bladder catheters. In hospitalized patients who require Foley catheters, the dilemma is further complicated; the daily risk for bacteriuria is 3%-7%, and catheter-associated bacteriuria is an infrequent cause of nosocomial fever.[6,7] The American College of Critical Care Medicine and Infectious Diseases Society of America recommend obtaining urine cultures only in certain cases for evaluation of fever in a catheterized critically ill patient: (1) kidney transplant recipients; (2) neutropenic patients; (3) patients who have recently undergone genitourinary surgery; and (4) patients with evidence of genitourinary obstruction.[8]

Established in 2015, the Hospital-Acquired Condition (HAC) Reduction Program is a Medicare pay-for-performance program that incentivizes hospitals to reduce the number of HACs. It links Medicare payments to healthcare quality. Individual hospital metrics are publicly reported and available here. Hospital infection preventionists (IPs) utilize specific surveillance definitions established by the Centers for Disease Control and Prevention National Healthcare Safety Network (NHSN) when making determinations of hospital-acquired infections. These include (1) catheter-associated urinary tract infection (CAUTI), (2) central line–associated bloodstream infection (CLABSI), (3) C difficile infection, (4) surgical-site infection, and (5) methicillin-resistant Staphylococcus aureus (MRSA) bacteremia.

The NHSN CAUTI definition lacks specificity and has been estimated to have a positive predictive value of 35% compared with an ID consultant's impression.[9] NHSN's definition is:

An indwelling catheter for at least 2 consecutive days, symptoms consistent with a UTI, and >100,000 colony forming units/mL of bacteria in a urine culture performed ≥48 hours after admission. Symptoms are considered at least 1 of fever >38°C, suprapubic tenderness, costovertebral angle pain or tenderness, urinary urgency, urinary frequency, or dysuria.[10]

The NHSN CAUTI definition does not allow for attribution of fever to an alternative diagnosis for surveillance purposes.[11] For example, if a "fever workup" yields MRSA in the blood and Escherichia coli in the urine (obtained in the presence of a Foley catheter for 3 days), the latter fulfills NHSN criteria as a reportable hospital-acquired infection, even though clinically the fever was due to the bacteremia. Unlike an NHSN CAUTI, a clinical CAUTI is a diagnosis of exclusion.

Despite implementing nursing best practices for insertion and removal, rates still may remain suboptimal because of a "culture" of pan culturing for fever workups. The phenomenon of pan culturing has come under scrutiny recently.[12] It lacks diagnostic specificity and carries the risk of misclassifying patients with infections they don't truly have. This may result in the delayed diagnosis of other causes of fever and exposure to unnecessary antimicrobials. It can also increase the diagnosis of NHSN CAUTIs and negatively affect an institution's HAC score, resulting in public misperceptions and financial penalties.

Incorporation of urine culture diagnostic stewardship into an existing best practice bundle has been shown to safely augment reductions in CAUTI rates and reduce unnecessary laboratory expenditures.[13,14,15,16] In the context of nonspecific surveillance definitions, patient safety, and value-based purchasing, diagnostic stewardship is here to stay.

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