Antimicrobial Stewardship Programs: Effects on Clinical and Economic Outcomes and Future Directions

Adverse Effects

Reduced toxicities and adverse effects are expected with reduced usage of antimicrobials. The systematic review conducted by Filice et al [24] examined the incidence of adverse effects related to antibiotic usage, and their findings suggest, at the least, that stewardship programs generally do not cause harm, as only 2 of the studies they examined reported adverse events. Following stewardship interventions, 5.5% of the patients deteriorated; and of those, the large majority (75%) deteriorated due to progression of oncological malignancies. To further illustrate the effect of stewardship interventions on toxicities and side effects of antimicrobials, Schuts et al demonstrated that the risk of nephrotoxicity while on antimicrobial therapy was reduced based on 14 studies of moderate heterogeneity as a result of an ASP (OR 0.46, 95% CI 0.28–0.77, P = 0.003; I ² = 34%) [39,44]. It is intuitive that reduced drug exposure results in reduced adverse effects, as such these results are expected.

Economic Outcomes

Although the focus of ASPs is often to improve clinical outcomes, economic outcomes are an important component of ASPs; these programs bring associated economic value that should be highlighted and further detailed [22,45,46]. Since clinical outcomes are often the main objective of ASPs, most available studies have been clinical effect studies (rather than economic analyses), in which economic assessments are often a secondary consideration, if included.

As a result, cost evaluations are conducted on direct cost reductions whereas indirect cost reductions are often not critically evaluated. ASPs reduce hospital expenditures by limiting hospital-acquired infections and the associated medical costs where they are effective at decreasing consumption of antimicrobials [22,45], and by reducing antibiotic misuse, iatrogenic infections, and the rates of antibiotic-resistant organisms [47]. In one retrospective observational study, annual costs of antibiotics dropped by 33% with re-implementation of an ASP, mirrored by an overall decrease in antibiotic consumption of about 10%, over the course of the intervention study period [30]. Of note is that at 1 year post-ASP re-implementation, antibiotic consumption actually increased (by 5.4%); however, because antibiotic usage had changed to more appropriate and cost-effective therapies, cost expenditures associated with antibiotics were still reduced by 13% for that year relative to pre-ASP re-implementation. Aside from economic evaluations centered on consumption rates, there is the potential to further evaluate economic benefits associated with stewardship when looking at other outcomes, including hospital LOS [22], as well as indirect costs such as morbidity and mortality, societal, and operational costs [46]. Currently, these detailed analyses are lacking. In conjunction with more standardized clinical metrics, these assessments are needed to better delineate the full cost effectiveness of ASPs.

Evidence Summary

The evidence for inpatient ASP effectiveness is promising but mixed. Much of the evidence is low-level, based on observational studies that are retrospective in nature, and systematic reviews and meta-analyses are based on these types of studies. Studies have been conducted over a range of years, and the duration of intervention periods often vary widely between studies; it is difficult to capture and account for all of the infection, prescribing, and drug availability patterns (as well as the intervention differences or new drug approvals) throughout these time periods. To complicate the matter, both the quality of data as well as the quality of the ASPs are highly variable.