Evolution of CAUTI: time for more inclusive metrics?

By Dr. Sonali D. Advani and Dr. Mohamad G. Fakih

Catheter-associated urinary tract infection (CAUTI) has long been considered a preventable healthcare-associated infection. Patients are at risk for catheter harm when they are admitted to a hospital, surgical centre, or long-term care facility, or evaluated in the outpatient setting. In the acute-care setting, 15–25 per cent of patients are exposed to a urinary catheter during their hospitalisation. Appropriate catheter use improves patient outcomes by releasing an underlying obstruction or providing accurate intake and output information for managing critically ill patients.

Historically, CAUTIs account for more than one-third of healthcare-associated infections (HAIs) reported by acute-care hospitals. With the recognition of colonisation in catheterised patients and surveillance definition changes, the proportion of CAUTIs relative to other HAIs has decreased.

HAI Metrics

The metrics used for measuring HAIs are important because these infections are publicly reported. A variety of metrics are used to track US healthcare-system performance related to CAUTIs. Since 2010, discrepancies in reductions have been reported based on the metric used.

However, the Centre for Disease Control and Prevention’s (CDC’s) National Healthcare Safety Network (NHSN) provides standardised surveillance definitions for all HAIs.

The inclusion of the NHSN CAUTI in the CMS hospital-acquired condition reduction programme has led to ubiquitous reliance on this performance metric. The standardized infection ratio (SIR), which is the ratio of observed to predicted NHSN CAUTI events, is the nationally used metric to gauge improvements in CAUTI prevention.

We propose 3 key metrics to align outcomes with interventions: the standardized utilization ratio (SUR), population SIR, and CA bacteriuria.

1. Device utilisation and Standardised Utilisation Ratio (SUR)

The risk of device harm is ongoing as long as the catheter is in use. Beyond focusing on reducing unnecessary catheter insertions and catheter days, utilisation is a process and outcome measure that reflects the risk of infectious and non-infectious sequel of catheter use. Device utilisation is an overall objective metric that captures potential catheter harm, but it does not measure appropriateness of use or duration of catheter use per patient. For example, the risk of CAUTI may be different in a unit with a single indwelling catheter for 10 days compared to a unit with 5 catheters for 2 days each, despite both units reporting the same device days (1 catheter×10 days = 5 catheters × 2 days = 10 catheter days).17 The recently introduced SUR helps identify whether a unit or a hospital uses more catheters than its comparators. The SUR is a ratio of observed to predicted device days and is compared to a national benchmark.

The SUR adjusts for hospital- and unit-level factors and may be used as a surrogate for potential catheter harm.

2. Population Standardized Infection Ratio (SIR)

The SIR or “device SIR” is a ratio of observed to predicted NHSN CAUTI events and is based on the number of actual observed catheter days for a specific unit. Both device SIR and SUR provide valuable information about a patient’s risk related to a urinary catheter. However, a metric that represents population risk can combine both elements. This is calculated as the ratio of observed to predicted NHSN-CAUTI events based on the predicted device
days (compared to device SIR which is based on actual device days).

This metric,“population SIR,” accounts for the risk of device exposure and infection to all patients. Importantly, both device SIR and population SIR use the NHSN CAUTI definition. However, population SIR will entice teams to also focus on noninfectious complications because it rewards hospitals that focus on device utilization. Population SIR can also better account for both, changes in device utilization and CAUTI risk over time.

3. Catheter-Associated Bacteriuria

Catheter-associated bacteriuria is common in patients with indwelling catheters and, in its vast majority, is asymptomatic.

Inappropriate antimicrobial exposure in patients with asymptomatic CA bacteriuria increases the risk for resistance, adverse drug events, and Clostridioides difficile colitis. Because the identification of CA bacteriuria is a key driver to inappropriate antibiotic use, including it as a performance metric may reduce catheter harm and support antimicrobial stewardship efforts.

Capturing CA bacteriuria can be fully automated from electronic medical records, and it can be risk adjusted similar to the standardized antibiotic administration ratio (SAAR). Tracking specific patients with CA bacteriuria that receive antimicrobial therapy may incorporate both diagnostic and antimicrobial stewardship, but it cannot distinguish whether antibiotics were prescribed for bacteriuria alone or an alternate source of infection, and this metric cannot be electronically captured. Process measures like SUR and CA bacteriuria can bring a fresh perspective to those leading quality efforts in acute care and can motivate decision makers to prioritize resources toward avoiding overall device harm and promoting stewardship.


Metrics have important implications on the perceived effectiveness of quality improvement efforts. Hospitals are currently incentivized to concentrate their efforts on preventing NHSN CAUTI events, rather than focusing on catheter harm. We advocate broadening the scope to include both infectious and noninfectious catheter complications, analogous to monitoring ventilator-associated events (VAEs).

Hospitals are now encouraged to perform surveillance for VAEs, which is a more inclusive outcome than ventilator-associated pneumonia.55 Evolving to more inclusive metrics provides greater opportunity to educate providers regarding appropriate device utilization and antimicrobial stewardship.

No single perfect metric to evaluate patient harm from CAUTIs exists due to the difficulty to clearly define its elements clinically.

Surveillance definitions have ranged from the broad definition of CA bacteriuria previously to a very narrow focus recently on high-level bacteriuria and fever. Due to limitations of the current metrics, the focus of quality improvement efforts has shifted to frequency of testing, particularly to how often urine cultures are done. If we expand the scope to all catheter harm, then the SUR would provide a good surrogate for preventable infectious and noninfectious catheter harm. Electronically captured CA bacteriuria adjusted to patient and hospital characteristics can help evaluate the component of testing stewardship. Finally, population SIR is an attractive metric that reflects both infectious and noninfectious harm because it captures efforts to optimize device use and care while adjusting for population risk. Future metrics should shift the focus from purely infection-related injury to all types of catheter-related harm, reflect frequency of testing, and should be electronically captured. Hence, our CAUTI performance metrics need to be refined so that our measurements reflect our efforts to improve patient outcomes.

About Authors:

Dr. Sonali D. Advani is Associate Medical Director for Infection Prevention at Yale New Haven Hospital.

Dr. Mohamad G. Fakih is Medical Director of Senior Medical Director, Care Excellence, Ascension Healthcare.

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