Antibiotic expected effectiveness and cost under real life microbiology: evaluation of ertapenem and ceftriaxone in the treatment of community-acquired pneumonia for elderly patients in Spain

Figures & data

Table 1 Efficacy and cost data for decision-tree model of CAP in Spain (base-case scenario)

	Ertapenem-arm	Ceftriaxone-arm	Source
Initial efficacy (clinical response) (mean, [95% CI])	0.936 (0.896–0.977)	0.913 (0.861–0.965)	Age >65 years subgroup based on Ortiz-Ruiz et al^Citation15
Second-line antibiotic efficacy (mean, [95% CI])	0.863 (0.811–0.915)	0.863 (0.811–0.915)	Romanelli et al^Citation18
Cost per day of first-line antibiotic treatment	€39.08	€7.20	Unit cost from Botplus;^Citation29 dose information from SEPAR guideline^Citation6
Cost per day of second-line antibiotic treatment (imipenem)	€40.38	€40.38	Unit cost from Botplus;^Citation29 dose information from SEPAR guideline^Citation6
Cost of hospitalization per day	€419.3	€419.3	Hospitalization cost based on weighted DRGs 89 and 90 from Spanish Ministry of Health^Citation27
Length of stay for patients with clinical success (mean, [95% CI])	8.4 (8.1–8.7) days	8.4 (8.1–8.7) days	Treatment duration based on Menéndez et al^Citation26 and DRGs update^Citation27
Length of stay for patients with clinical failure (mean, [95% CI])	16.5 (14.8–18.2) days	16.5 (14.8–18.2) days	Treatment duration based on Menéndez et al^Citation26 and DRGs update^Citation27

Abbreviations: CAP, community-acquired pneumonia; CI, confidence interval; DRGs, diagnosis-related groups; SEPAR, Spanish Society of Chest Disease and Thoracic Surgery.

Table 2 Initial efficacy, overall susceptibility, and expected effectiveness for ertapenem, ceftriaxone, and imipenem (base-case scenario)

	Ertapenem	Ceftriaxone	Imipenem
Initial efficacy	0.94	0.91	0.88
Estimated overall susceptibility	0.76	0.71	0.78
Expected effectiveness	0.71	0.65	0.69

Notes: Estimated overall susceptibility is the ∑ % pathogen’s distribution_i • % pathogen’s susceptibility_i; Expected effectiveness is initial efficacy • estimated overall susceptibility.

Figure 1 Decision-tree model for treatment of community acquired pneumonia (CAP).

Table 3 Probability estimates, ranges, and distribution parameters used in the model (base-case scenario)

Expected effectiveness	Estimate	Range		Parameters
		Low	High	SE	Alpha	Beta
Ertapenem	0.71	0.68	0.74	0.02	603.00	246.30
Ceftriaxone	0.648	0.61	0.68	0.02	414.12	224.95
Second-line treatment	0.682	0.61	0.75	0.03	121.48	56.64
Mortality	0.22	0.14	0.30	0.04	23.87	84.64
Treatment duration and LOS for patients with clinical success	8.4	8.1	8.7	–	–	–
Treatment duration and LOS for patients with clinical failure	16.5	14.8	18.2	–	–	–

Abbreviations: LOS, length of hospital stay; SE, standard error.

Figure 2 Drug and resource costs per patient for ertapenem- and ceftriaxone-arm (base-case scenario).

Table 4 Clinical and economic results of the model for the base-case scenario

	Ertapenem-arm	Ceftriaxone-arm	Differences
First-line clinical failures avoided	71.0%	64.8%	6.2%
Cost per patient
Drug cost per patient	€426	€243	€183
Resource use cost per patient	€4,514	€4,726	−€212
Total cost	€4,940	€4,969	−€29

Note: The base-case scenario assumed that data from the initial clinical efficacy of ertapenem and of ceftriaxone are based on Ortiz-Ruiz et al.¹⁵

Table 5 Clinical and economic results of the model for the alternative scenario

	PSI ≤3			PSI >3
	Ertapenem-arm	Ceftriaxone-arm	Differences	Ertapenem-arm	Ceftriaxone-arm	Differences
First-line clinical failures avoided	70.3%	66.5%	3.8%	68.3%	61.8%	6.5%
Cost per patient
Drug cost per patient	€428	€234	€194	€435	€259	€176
Resource use cost per patient	€4,537	€4,665	−€128	€4,607	€4,827	−€220
Total cost	€4,965	€4,899	€66	€5,042	€5,086	−€44

Note: The alternative scenario was developed using the clinical data of clinical cure rates for patients with PSI ≤3 and PSI >3 from the combined analyses performed by Ortiz-Ruiz et al.¹⁵

Abbreviation: PSI, pneumonia severity index.

Figure 3 One-way sensitivity analysis for length of stay.

Notes: (A) LOS decreases at the same rate for first- and second-line treatment. (B) LOS decreases to a greater extent for the first line treatment. (C) LOS decreases to a greater extent for the second line treatment.
Abbreviation: LOS, length of hospital stay.

Figure 4 Tornado diagram for the base-case.

Abbreviation: BC, base-case.

Figure 5 Cost-effectiveness plot for the base-case scenario (>65 years) comparing ertapenem versus ceftriaxone.

Notes: The figure shows the incremental cost-effectiveness scatter plot derived from the probabilistic sensitivity analysis. Each blue dot represents the result of an iteration of the Monte Carlo simulation. The red dot is the average of the 1,000 iterations.

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