Table 2.

Proposed method that could be undertaken by healthcare organizations to incorporate externalities associated with antimicrobial use

Measurements required	Description	Data sources
Strategy description and costs	Describe the strategy to contain antimicrobial resistance by reducing the use of antimicrobials in hospitals. Describe all costs associated with implementing and running the program for a minimum of 2 years.	Existing Antimicrobial Stewardship programs, Pharmacy Services, Financial departments
Baseline rate of antimicrobial resistant organism	Rates of hospital-acquired, healthcare associated or community-acquired infections due to antimicrobial resistant organisms in the healthcare facility	Infection Prevention and Control Laboratory microbiology data linked to Discharge Abstract Databases
Strategy effectiveness	Policy effectiveness would be measured by the change in the dose-response relationship (elasticity) between antimicrobial consumption and the emergence of resistance using multivariate time series analyses accounting for different factors related to transmission of the antimicrobial resistant organism. The model coefficients would demonstrate that temporal increases/decreases in the volume of antimicrobial use are followed by temporal increases/decreases in the incidence of hospital acquired antimicrobial resistant organism.	Infection Prevention and Control Laboratory microbiology linked to Discharge Abstract Databases Antimicrobial utilization from patient management systems or pharmacy prescribing systems
Incremental cost of Antimicrobial resistant infections	The incremental costs of infections with antimicrobial resistant organisms is required whereby systematic differences between patients with and without the infection are accounted for. These differences can be accounted for by a particular epidemiologic study design (i.e. matching) or through statistical modeling techniques. There is a paucity of studies currently that appropriately evaluate the true incremental costs of these infections and which consider the time-varying nature of healthcare-associated infectionsa	Hospital financial departments with micro-costing data on costs/charges of patients with and without infections with an antimicrobial resistant organism.
Economic evaluation of the strategy	A simple decision analytic model to compare the costs of the policy with the costs saved through reducing antimicrobial resistant organisms (the negative externality). It would evaluate the change in the dose-response relationship between antimicrobial use and antimicrobial resistance as a result of the policy. The time horizon would be a minimum of 2 years to observe changes in antimicrobial resistance rates as a result of reduced prescribing.

^aThis concept is further discussed in the section “Ways to Measure Externalities of Antimicrobial Use”