By Kalvin Yu, MD, FIDSA, Vice President of North America Medical Affairs

The National Healthcare Safety Network (NHSN) of the Centers for Disease Control and Prevention (CDC) is the most broadly used system in the United States to track healthcare-associated infections (HAIs). Using endorsed quality measures, NHSN monitors healthcare-associated infections and other patient safety-related metrics to assess the success of prevention initiatives and eliminate HAIs.  

Healthcare facilities in the U.S. are required by law to report certain HAIs to the NHSN, such as:

• Central line-associated bloodstream infection (CLABSI)
• Catheter-associated urinary tract infection (CAUTI)
• Surgical Site Infection (SSI)
• Hospital-onset Clostridium difficile infection (CDI)
• MRSA Bacteremia

CLABSI, with a requirement to link an infection in the blood with a central line source, represents a subtype of hospital onset bloodstream infection, and is one of several potential sources of bloodstream infections (BSI) among hospitalized patients. When a BSI is diagnosed on or after day four of a patient’s hospital admission, it is designated as a hospital-onset bacteremia or fungemia (HOB).

Unlike CLABSI, HOB is currently not a mandatory CMS quality measure and, as a result, there has been limited data on the clinical and financial burden related to HOB. Nevertheless, clinicians are aware of the morbidity resulting from HOB events, and improving clinical outcomes in patients with HOB is an area of interest for clinicians and healthcare system administrators alike. This has led to the proposed HOB quality metric which received a positive recommendation from the National Quality Forum (NQF) Patient Safety Committee and Battelle review in early and mid-2023, respectively.

The proposed HOB measure is broader and encompasses hospital bloodstream infections from multiple sources, including CLABSIs. This focus on broader sources of bloodstream infections has the potential to increase attention on infection prevention, and link diagnostic stewardship with antibiotic stewardship.

As an example, reduction of total BSIs through prevention efforts, coupled with more timely isolation and definitive therapy of bloodstream infections when they do occur may positively influence patient outcomes. A survey conducted by the American Hospital Association on HOB revealed that the more than 200 clinician and healthcare administrator respondents believed that approximately 40 percent of the time, definitive therapy was started more than 24 hours after the blood specimen for diagnosis was taken. This delay could have adverse ramifications on patient care.

In fact, a recent publication documented that inadequate empiric therapy (IET) is prescribed 20 percent of the time when an infection occurs, and that longer IET is associated with increased length of stay, mortality risk and cost of care. Furthermore, with antimicrobial stewardship programs now required in the US, there is  an infrastructure to also achieve better diagnostic stewardship which may decrease the utilization of antibiotics and, potentially, the rates of antimicrobial resistance.

To assess the extent of HOB’s impact on patients and healthcare systems, we conducted a retrospective observational study of patients in 41 acute-care hospitals. CLABSI cases were defined as those reported to the NHSN. HOB was defined as a positive blood culture with an eligible bloodstream organism collected during the hospital-onset period (i.e., on or after day 4). We evaluated patient characteristics, other positive cultures (urine, respiratory, or skin and soft tissue), and microorganisms in a cross-sectional analysis cohort. We explored adjusted patient outcomes, including length of stay (LOS), hospital cost, and mortality.

Our key findings include:

• HOB rates are at least four times higher than CLABSI rates.
• HOB events have a three times higher mortality rate in patients with an ICU encounter, a higher risk of readmission, higher costs ($25,000 to $55,000 more per admission), significantly longer length of stay (12 to 17 days average increase length of stay, compared to 1:5 control case matching).  
• Most sources of HOB come from urinary and respiratory sources, as well as primary bloodstream infections and other HAIs.
• These data suggest that HOB is a more inclusive quality metric that captures more BSI patients than the current CLABSI-reportable events.
• The new proposed metric bypasses the requirement to adjudicate each event, as is currently mandated for CLABSI reporting and the need to link the BSI to a central line as the primary source. This more automated metric therefore could save time for infection preventionists for other duties such as on the floor education with nursing staff and more direct links to improving patient care.  
• The more inclusive proposed HOB metric may help bring visibility to the need of optimal and timely definitive therapy for BSIs and the development of innovative prevention measures based on a broad range of possible sources of HOB infections.

Like CLABSIs, HOB events have serious clinical ramifications on patient outcomes, length of hospital stay, and cost. According to published studies, major sources of HOB are potentially preventable with basic practice improvements addressing infection risk factors, such as adherence to correct device insertion and maintenance practices, hand hygiene compliance, rapid and accurate pathogen identification and surgical site preparation practices.

These findings highlight the importance of mitigating risk factors associated with HOB, best practices in identifying pathogens, and improving time to definitive antimicrobial therapy through existing required infection prevention and antimicrobial stewardship programs to improve clinical outcomes and patient safety.