In this edition of the journal, Yadav and colleagues describe original research comparing cost differences for two different outpatient parenteral antibiotic therapy (OPAT) approaches with inpatient hospitalisation for patients with cellulitis requiring intravenous (IV) antibiotics [1]. Emergency physicians are very familiar with this patient group and over the last two decades, many outpatient management strategies have been implemented [2]. The exact format of such strategies is often dependent upon health system structure and funding mechanisms. For example, in some countries such as Australia, forms of “hospital in the home” have been created to provide IV antibiotics in the community, which are hospital outreach services as opposed to care delivered by community health service providers. In the example of Australia, this comes about because funding for secondary care occurs at a state (or provincial) level, whereas funding for primary care is provided by central government, which makes cost sharing and movement challenging.

The two OPAT strategies described and studied here are: (a) OPAT Clinic—Provision of IV antibiotics at a community care access centre (which is an outpatient home and community care service provided by the local health integration network). Home visit administration was also possible. Patients were reviewed at an OPAT clinic where they were assessed by an infectious diseases physician, and (b) “Return to ED”—This had similar community care access centre IV antibiotic administration. There was no planned OPAT Clinic follow-up, but patients were able to follow up at the ED for review if needed.

The authors compared direct (fee-code-linked hospital expenses) and indirect (overhead-related) costings. Perhaps unsurprisingly, the mean total cost of care was significantly higher for hospital admission ($10,145) compared with outpatient strategies—OPAT Clinic ($2,170) and “Return to ED” ($1493). The investigators conclude that an outpatient approach should be the preferred strategy over inpatient care. They also highlight that while an OPAT Clinic could save the health system money (compared to inpatient admission), it is more expensive than a “Return to ED” strategy.

There is a very useful costing analysis that will be of interest to those wishing to staff or review an outpatient antibiotic service and have added additional commentary to the challenges of collecting such costs. The costing perspective taken for this study is that of the health system—considering the costs of providing care to people under different models. Future analysis could also consider costs from a patient perspective, exploring both financial and other forms of cost to a patient under the different models of care, for example.

Also of note is that this was not a randomised study and the patients in the hospital group appear to be notably more challenging with higher age and comorbidities. This may have contributed to the increased costs associated with hospital admission. The issue of comorbidities also plays out more generally in the cost results—the regression analysis of incremental cost for OPAT Clinic vs return to ED shows that some comorbidities, and having a prior history of cellulitis, can have a substantial impact on the cost of treating the patient. In some cases, these costs are actually larger than the difference in cost between treatment settings. Comorbidity has been shown to have a major impact on the cost of health care in many settings, including Canada [3]. There is scope to explore the impact of comorbidities on the cost of providing acute and episodic care in emergency room and community settings. Such analysis has the potential to contribute to a better understanding of patterns of health need and inequality in the population, and to reveal where health system resources are needed. The interesting example in the present research also makes clear that the cost impact of prevention is increased when comorbidities are present.

While this study focuses on IV community antibiotics, there is now increasing interest in enhanced oral antibiotic strategies. The key determinant of impact on the infection are the antibiotic concentrations attained from the regimen. The minimum inhibitory concentration (MIC) is the lowest concentration of antibiotic which prevents visible growth of bacteria. For beta-lactam antibiotics, the time that concentrations exceed the MIC (or T > MIC) over the dose interval is an important predictor of antibacterial effect. Oral antibiotic regimens that achieve equivalent T > MIC to IV treatment are expected to be associated with the same clinical outcome. Improved MIC target attainment and reduced dosing intervals of antibiotics such as flucloxacillin can be achieved by combination with oral probenecid. Research has shown that T > MIC can be attained using flucloxacillin 1000 mg and probenecid 500 mg three times a day (no special timing in association with food is required) [4, 5]. The use of probenecid enhanced oral antibiotic regimens in place of IV antibiotic treatment is now utilised in a number of places. In addition to reducing antibiotic costs such an approach can be self-administered and is more convenient for the patient. Further work is expected in this space.

Identifying and initiating outpatient-based management for patients with cellulitis is an excellent example of how Emergency Medicine can be involved in safely making a meaningful impact to hospital admissions and patient convenience. This study makes a useful quantification of how much money can potentially be saved using this approach and compares the costs of two potential strategies. It also provides further opportunities to explore the complex manner in which the costs of health services play out in different settings.