Multistate modelling to estimate excess length of stay and risk of death associated with organ/space infection after elective colorectal surgery
Introduction
Surgical site infections (SSIs) are one of the most severe and dreaded healthcare-associated infections (HCAIs) in elective colorectal surgery (ECS). These infections increase morbidity and mortality, and prolong length of stay (LOS), thereby increasing patient and health costs [1], [2]. Among SSIs, organ/space (OS)-SSI has been associated with the worst outcomes [3], [4], [5].
Since colorectal surgery is a cornerstone of treatment for colorectal cancer – the third most common cancer diagnosed in developed countries – avoiding these HCAIs is an urgent matter. Multiple strategies have been shown to be successful in preventing SSIs; however, recent studies still show high rates of OS-SSI associated with colorectal surgery [6], [7], [8], [9], [10], [11], [12], [13].
Measuring the health cost of OS-SSI accurately can facilitate joint efforts by all stakeholders to implement targeted prevention strategies. Currently, from the hospital perspective, the cost of HCAIs is mostly due to extending patient LOS, which determines missed new hospital admissions [14], [15]. When estimating LOS due to HCAIs, applying statistical models that consider the time-dependent nature of the infection has been recommended. This approach permits a better control of time-dependent bias and avoids overestimation of excess LOS [16], [17].
To date, studies reporting the effect of SSI on LOS in colorectal surgery have not considered time-dependent bias [1], [4], [12]. The purpose of the present study is therefore to assess the health costs of OS-SSI measured in terms of excess LOS and risk of death during the hospital stay in a prospective cohort of patients undergoing ECS, taking into account timing of infection and competing events.
Section snippets
Setting and study design
This was a multicentre prospective cohort study of adult (aged ≥18 years) patients who underwent ECS from January 2012 to December 2014, at 10 hospitals in Catalonia, Spain. The hospital characteristics are shown in Table I. All these hospitals routinely report data to the regional surveillance programme for HCAIs: VINCat [5], [18]. All patients hospitalized for ECS at the different hospitals were followed up until discharge or death. Patients with pre-existing infection at the time of surgery
Results
A total of 2778 patients were included in the cohort; cancer was the main cause of surgery 2623 (94%). During the hospital stay, 343 patients (12.3%) developed SSI. Of those, 194 (7%) had OS-SSI and 149 (5.3%) incisional SSI. The incidence density of overall SSI was 15.7 per 1000 patient-days at risk; 8.9 and 6.8 per 1000 patient-days at risk for OS-SSI and incisional SSI, respectively. Infection occurred in a median time of six days after surgery for both OS-SSI and incisional SSI. The median
Discussion
This study shows that, among SSIs, OS-SSI had the greatest burden on LOS and mortality in patients undergoing ECS in a large cohort of patients. The results are consistent with those reported in the literature; however, previous studies frequently used matching designs to estimate excess LOS, a type of design that overestimates LOS, since they do not consider time-dependency of the infection [1], [4], [23], [24], [25], [26].
Excess LOS attributed to SSI varies from 4.1 to 15 days, although most
Acknowledgements
We would like to thank the other researchers and members of the VINCat colon surgery group: Hospital Bellvitge: D. Camprubí; Hospital de Viladecans: L. Martín, C. Sanz; Consorci Sanitari de l’Anoia: M Brugués; Corporació Saniària Parc Taulí: X. Serra-Aracil, L. Mora; Parc Sanitari Sant Joan de Déu de Sant Boi: V. Diaz-Brito, E. Moreno; Fundació Althaia: F. Obradors; Consorci Sanitari de Terrassa: E. Espejo, F. Aguilar, L. Pagespetit; Hospital Universitari Mútua de Terrassa: C. Nicolás, A.
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Members of the VINCat colon surgery group are listed in the Acknowledgements section.