Background and Objective:
Antimicrobial resistance (AMR) is an important public health problem with a strong epidemiological, economic, and social impact. The objective of this analysis was to evaluate the cost-effectiveness of imipenem/cilastatin/relebactam treatment compared to colistin-imipenem in the treatment of hospitalized patients with gram-negative bacterial infection caused by imipenem-resistant pathogens.

Methodology:
To simulate a cohort of patients a mixed model was developed, structured in two sections for simulation in the methodology short and long-term evolution of the patients in analysis. Modelled patients were those with hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia (HABP/VABP), complicated intra-abdominal infection (cIAI) or complicated urinal tract infection (cUTI) caused by carbapenem-resistant Gram-negative (GN) pathogens. The model begins with a short-term decision tree describing possible treatment routes and outcomes for patients during the hospitalization period. After treatment, patients are classified as cured, not cured or dead (the proportion of which depends on the data on the efficacy and mortality of the treatments). Patients who have not recovered from the initial treatment remain to receive a subsequent line of therapy. Those who are alive but not cured at the end of the decision tree are assumed to die within one year, which is broadly in line with clinical expert opinion. Patients who are healed in the decision tree in the long-term Markov model, designed to capture the follow-up costs and health-related quality of life (HRQL) of patients healed over their lifetime.

Results:
The analysis, conducted on a hypothetical cohort of 1000 patients, highlights how imipenem/cilastatin/relebactam is advantageous. In fact, it is dominant compared to colistin-imipenem both in the National Health Sistem (NHS) and in the social perspective since, compared to an average saving of € 2,800.15 and € 3,174.63 respectively, it would generate an increase of 4.76 years of life and 4.12 quality-adjusted life years (QALY) per patient.