Modeling operational quality metrics and costs of long-acting antibiotics for acute bacterial skin and skin structure infection treatment in the emergency department

Figures & data

Figure 1. Overview of model steps and patient flow. All care pathways have the same basic flow through the model: patients enter ED; after registration, patients enter (1) waiting room, then (2) triage before being provided (3) an ED bed. Patients are then either discharged from ED to home, or to (4) observation or (5) are admitted to hospital; patients who go to (4) observation are either discharged home or (5) admitted to hospital; as patients flow through, the ED is modeled according to patient acuity; more severe patients follow an abbreviated path. Abbreviations. BCU, Biocontainment unit; DAL, Dalbavancin; ED, Emergency department; ORI, Oritavancin; VAN, Vancomycin. *Patients treated with DAL/ORI discharged home from ED. ^†Patients treated with VAN may go to observation¹¹ and then are either discharged home or admitted to hospital.

Table 1. Model patient and resource inputs.

Parameter	Parameter values
Patient arrival patterns	4.1 patients/h average^26^,^29^,a
ABSSSI vs. non-ABSSSI patients	3.7% ABSSSI; 96.3% non-ABSSSI^28
Acute vs. nonacute patients^b	10% acute patients; 90% nonacute patients
Resources, n (average)
ED beds	21^26
Observation beds	6^12
Nurses	6^26
Triage nurses	2^26
Physicians	2^26
Patient process steps (average time, min)
Registration	14^26
Triage	13^26
Nurse assessment	8^26
Physician assessment	8^26
Physician assessment of patient response	15^26
Nurse processing of admission	40^26
Nurse processing of discharge	15^26
Patient willingness to wait^c
0–2 h	51%^30
2–8 h	17%^30
No limit	32%^30
ABSSSI patient treatment time
Dalbavancin	30 min, single dose^15
Oritavancin	3 h, single dose^31
Vancomycin	1 h, twice daily^10^,d
Observation LOS (patients receiving vancomycin only)	24 h average^12^,e
Non-ABSSSI patient treatment time	90 min^32
ABSSSI patient disposition from ED
Treated with LA
Admitted to hospital	–
Discharged to observation	–
Discharged home	100% (expert opinion)
Treated with vancomycin
Admitted to hospital	40%^4^,^33
Discharged to observation	30% (expert opinion)
Discharged home	30% (expert opinion)
Non-ABSSSI patient disposition from ED
Admitted to hospital	27%^34
Discharged home	73% (expert opinion)
ABSSSI patient disposition from observation
Treated with LA
Admitted to hospital	–
Discharged home	–
Treated with vancomycin
Admitted to hospital	10% (expert opinion)
Discharged home	90% (expert opinion)
Non-ABSSSI patient disposition from observation
Admitted to hospital	–
Discharged home	–

Abbreviations. ABSSSI, Acute bacterial skin and skin structure infection; ED, Emergency department; LA, Long-acting antibiotic; LOS, Length of stay.

^a Derived from the average of 36,342 annual arrival data for an average US hospital^26,35.

^b Acute patients skip registration and triage process steps; expert opinion based on studies that were similarly structured^21,22.

^c Used to calculate percentage of patients leaving without being seen.

^d Patient stayed in ED for first dose only.

^e Rounded up to one full day (24 h) from 22.3-h US average.

Table 2. Model inputs: cost of ABSSSI treatment.

Type of cost	Cost (in 2017 US dollars)^a
Medication cost^36	Vancomycin: $5 per dose^b Dalbavancin ($1490 per 500 mg vial): $4470 per dose Oritavancin: $2900 per dose
ED visit^c	$360.50 (CPT 99284/APC 615)^37
Observation time^d	$55.57 per hour under observation (APC 8009)^37 $1333.58 per 24 h period under observation (reference)^37
IV preparation	$5.83^38
IV administration	$187.48 for the first hour (vancomycin and dalbavancin) (CPT codes 96365 and 96366)^37 $35.19 per additional hour (vancomycin) $257.85 for oritavancin (3 h infusion)
PICC placement	$1042.44^e
Monitoring (labs)	Renal panel: $15.22^f Vancomycin trough levels: $23.74
Total cost per ABSSSI patient	Vancomycin: $1095 Dalbavancin: $5024 Oritavancin: $3526

Abbreviations. ABSSSI, Acute bacterial skin and skin structure infection; APC, Ambulatory Payment Classification; CPT, Current Procedural Terminology; ED, Emergency department; HCPCS, Healthcare Common Procedure Coding System; IV, Intravenous; PICC, Peripherally inserted central catheter.

^a Costs given in the sources were inflated to 2017 equivalents.

^b Per treatment based on wholesale acquisition cost pricing. Cost of all medications represents pricing before the application of any discounts or rebates.

^c 2015 codes were used although an updated 2017 coding guidance was available³³; the 2017 guidance has observation billed under Comprehensive Observation Services APC 8011 and hourly observation rate at HCPCS code G0378. However, 2015 codes were leveraged because rate has likely remained unchanged.

^d ED and observation have separate reimbursement codes.

^e Based on expert review, for ABSSSI patients receiving vancomycin, it was assumed that 50% of all patients receiving vancomycin would require a PICC to receive IV antibiotic therapy; cost of placement and complications would be ED costs¹⁷.

^f Based on expert review, ABSSSI patients receiving vancomycin would receive one renal panel per day and one vancomycin trough level after treatment once four doses were received in the ED and observation unit¹⁷.

Table 3. ED and observation unit setting metrics.

Outcome	Description
Patient-level variables (units)
ED/observation unit throughput rate	Standardized comparison of the rate at which patients receive treatment and are discharged home or admitted to hospital, with units (dispositions/ED and observation unit day)
ED/observation unit LOS	Time from patient arrival to the ED to either discharge home or hospital admission
ED wait time	Time from patient presentation (arrival) to the ED to initial assessment from the doctor
LWBS rate	Proportion of number of patients who leave the ED before seeing a doctor to the number of patients who present to the ED
Hospital admission rate	Number of patients who are admitted to the hospital divided by the number of patients who are treated
Annual variables
Annual ED/observation unit bed time	Time from patient obtaining an ED bed to either discharge home or hospital admission
Annual ED/observation unit nurse time	Nurse time spent providing care
Annual ED/observation unit physician time	Physician time spent providing care

Abbreviations. ED, Emergency department; LOS, Length of stay; LWBS, Left without being seen.

Figure 2. One-way sensitivity analysis results: tornado diagrams of (A) patient presentation rate, (B) ABSSSI patient presentation rate, (C) acute patient presentation rate, (D) ED nurse count, (E) physician count and (F) ED bed count. To allow extreme values generated by the sensitivity analysis to be plotted on the same tornado diagram, results were normalized by the average result for the base scenario (which was set to 1). Abbreviations. ABSSSI, Acute bacterial skin and skin structure infection; ED, Emergency department; LOS, Length of stay; LWBS, Left without being seen.

Table 4. Key ED outcomes and cost of treatment for ABSSSI patients.

	LA pathway	Standard care (vancomycin)	Difference (LA − standard care)	Relative difference
Outcome
ED/observation unit throughput rate (dispositions/ED and observation unit day)	10.31	2.26	+8.05	+356%
ED wait time (minutes/patient)	9.28	9.23	+0.10	+0.566%
ED/observation unit LOS (hours/patient)	3.45	10.6	−7.20	−68%
LWBS rate (%)	2.23	2.25	+0.02	+0.5%
Cost of ABSSSI treatment
Average cost/patient	$4275^a	$1095	$3180	+290%

Abbreviations. ABSSSI, Acute bacterial skin and skin structure infection; ED, Emergency department; LA, Long-acting antibiotic; LOS, Length of stay; LWBS, Left without being seen.

^a Average cost of the dalbavancin and oritavancin pathways (Table 2).

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Data availability statement

The data that support the findings of this study are available from the corresponding author, Katelyn R. Keyloun, upon request.