Even in the best-performing healthcare organization, there is always room for improving the quality of patient care and health outcomes.
Committing to continuous improvement is a key element to delivering quality patient care, but it’s also an expectation from accreditation and regulatory bodies, such as the Joint Commission which explicitly states in its Antimicrobial Stewardship standard MM.09.01.01, element of performance 21:
The hospital takes action on improvement opportunities identified by the antibiotic stewardship program.
Some common models, such as Plan-Do-Study-Act (PDSA) cycle, emphasize continuous improvement with iterative cycles, whereas LEAN and Six Sigma focus on reducing waste and standardizing processes to minimize defects. For antimicrobial stewardship (AMS), the CDC introduced a Target-Assess-Steward (TAS) model to provide a framework for improvement in antimicrobial use. In this article, we will discuss how to adopt the TAS framework through some concrete examples to improve antimicrobial utilization.
The TAS framework and metrics for improvement in antimicrobial use
The TAS framework comprises of three different components to help AMS leaders work methodically to improve antimicrobial use in their organizations.
Target
In the Target step, facilities that submit antimicrobial use and resistance (AUR) data to NHSN can obtain metrics such as standardized antimicrobial administration ratio (SAAR) and antimicrobial use cumulative attributable difference (AU-CAD) to help them identify opportunities for improvement.
SAAR is a ratio that compares a facility’s antimicrobial use to a standard referent population that has been statistically adjusted to account for the hospital’s unique characteristics in order to provide as close to a benchmark as possible with the available data. It is obtained by dividing a hospital’s actual antimicrobial utilization by the predicted antimicrobial utilization. As such a SAAR of 1 means that the hospital’s usage of antimicrobial is exactly the same as the predicted utilization, whereas a SAAR greater than 1 indicates the hospital’s usage is greater than expected. SAARs are available in adult, pediatric, and neonatal populations and are further separated by drug classes and patient care locations. Note that SAARs are not available in all NHSN-defined patient care locations, where insufficient national data exist to provide a denominator in the ratio calculation.
The CDC introduced a new metric called AU-CAD in 2022. Mathematically, AU-CAD is the difference in the number of days of therapy (DOT) between the hospital’s current state of antimicrobial use and the desired state of antimicrobial use based on its selected SAAR target. The calculation can be represented by the following equation:
AU-CAD = Observed antimicrobial days – (predicted antimicrobial days x SAAR target)
AU-CAD can be calculated for each SAAR antimicrobial group and patient care location in the NHSN AU module. Based on the equation presented above, a positive AU-CAD value indicates that your current SAAR value for the antimicrobial group selected is greater than your target SAAR. The AU-CAD number will then represent the number of DOTs you would have to reduce to reach the SAAR target. AU-CAD provides you with numeric target DOTs that you should reduce to reach your goal.
AU-CAD should be interpreted based on a defined period of time. For example, the observed antimicrobial days and predicted antimicrobial days may represent usage over 12 months, and then the AU-CAD will represent the number of DOTs that have to be decreased or increased over 12 months to reach the target SAAR. There is no national goal for SAAR and each facility may select a target SAAR based on historical trends, organizational and clinical priorities, resistance patterns, and other local factors.
Assess
As a reminder, metrics such as SAAR and AU-CAD simply compare your actual antimicrobial utilization to predicted antimicrobial utilization based on statistical adjustments to account for your hospital’s attributes and types of patients served. However, these metrics do NOT measure the appropriateness of antimicrobial prescribing. Once AMS leaders use SAAR and AU-CAD to identify locations and/or drug groups to target their efforts, they will need to assess the prescribing of antimicrobials to determine if there are gaps and opportunities to improve. Such assessment would typically involve methods such as Medication Use Evaluation.
Steward
Once AMS leaders identify the opportunities and gaps, we recommend convening relevant stakeholders such as prescribers, nurses, and microbiology personnel to design systemic interventions to improve antimicrobial use. Leaders will need to periodically monitor process and outcome metrics to ensure that the interventions are implemented and executed consistently and that the antimicrobial usage is trending in the right direction.
Putting TAS framework into practice
While there are only 3 steps in the TAS improvement model, the volume of available data can appear overwhelming at first. Let’s walk through a hypothetical example of how an AMS leader can take advantage of the data provided by NHSN to drive improvement.
Target
In this facility, as we can observe in the SAAR by Antimicrobial Category graph, most of the SAARs are around or below 1. The group with the highest SAAR is broad-spectrum agents typically used for hospital-onset infections. Over the past year, this group has a SAAR of 1.25 and was consistently above 1 every month. Thus the AMS leader should focus on this drug group based on the TAS model.
The next step is to assess which antimicrobial agents and which patient care locations are driving this elevated SAAR for the hospital. As shown in the Antimicrobial Use by Agent pie chart, piperacillin-tazobactam, and meropenem contributed 50% and 33% of DOTs to this category, respectively.
The AMS leader may also examine the specific patient care locations that the highest SAARs, in this case the top 3 locations include Peds Med Surg, Med 5, and Med 2 units in this fictitious hospital.
