https://orcid.org/0000-0003-2371-0999
Abstract
Objectives
This study aimed to review the characteristics of patients admitted with septic arthritis in Spanish hospitals and to measure the associated direct medical costs.
Methods
Hospital admission records of patients with septic arthritis as a primary diagnosis registered between 2010 and 2019 were evaluated in a retrospective study. Admission cost in the database is based on the diagnosis-related group-based hospital payment systems, determined by the Spanish Ministry of Health.
Results
Files from 16,438 patients were evaluated; median age was 56 years and 62.8% of patients were males. Staphylococcus was the most frequently registered pathogen, and 2.7% of admissions registered an antibiotic-resistant infection. Median hospitalization time was 14 days for adult patients and 8 days for children, with an in-hospital mortality rate of 3.7% for adult patients, and no deaths registered in children. The median length of intensive care unit (ICU) stay was 3 days. The mean admission cost was €6,382 per patient, with no significant differences between age groups. Admission costs increased significantly with the length of hospital stay. The total medical cost reached 12.7 million euros per year, considering all patients in the database.
Conclusions
This study provides new data on the medical costs of septic arthritis in Spain, providing a basis for the revision of resource allocation decisions in order to reduce the burden of this condition at the healthcare system level. Further research will be required to quantify the total burden associated with this condition.
Introduction
Septic arthritis is an uncommon cause of joint swelling and monoarticular arthritisCitation1. Data suggests that the frequency of septic arthritis could be increasing; the estimated incidence in the general population is 2–6 per 100,000 persons-year, while in the pediatric population it is 1–5 per 100,000, in developed countriesCitation1–3. These infections remain a challenge in terms of diagnosis and management, especially in children, considering that they can lead to long-lasting sequelaeCitation2,Citation4. In addition, when inadequately treated, septic arthritis can cause irreversible joint damage and disabilityCitation5. Hence, a rapid diagnosis is critical to reducing the risk of morbidity and mortality, and it is crucial to select an appropriate antimicrobial and a joint fluid drainage method after arthrocentesis; antibiotics are often required for 8 to 10 weeks, and drainage options include needle, arthroscopic or open drainageCitation6,Citation7.
Few data is available concerning the burden of septic arthritis in Spain, where diagnosis and management guidelines adjust to global strategiesCitation8. Evidence suggests a situation in Spain similar to that in other developed countries; the incidence of septic arthritis in one Spanish region was 3.1 per 100,000 persons the year 2000, and the knee has been reported as the most commonly involved jointCitation9,Citation10. Yet, the medical cost associated with septic arthritis has not been quantified and little data is available assessing the economic aspect of these infections. The aim of this study was to evaluate the characteristics of patients admitted with septic arthritis in Spanish hospitals between 2010 and 2019 and to quantify the associated medical costs.
Methods
Study design
Records of both ambulatory and inpatient admissions were obtained from a Spanish National discharge database and analyzed in a retrospective multicenter study. The database covers 90% of hospitals in Spain with data from all Spanish regions and is codified at the hospital level by means of the International Statistical Classification of Diseases and Related Health Problems, 9th version (ICD-9) prior to 2016 and 10th version (ICD-10) after the year 2016Citation11–13. Data within the database Centers are responsible for data codification, evaluation and confidentiality. The database is validated internally and subjected to periodic audits; in this process, errors and unreliable data are eliminated. The data inclusion period was from 1 Jan 2010 to 31 Dec 2019.
Data extraction
The records of both ambulatory visits and hospital admissions in which septic arthritis was registered as the admission motive (primary diagnosis) were claimed using the corresponding ICD-9 and ICD-10 codes: 711 and M00, respectively. Any cases associated with prosthetic joint infections were excluded. No parameters identifying healthcare centers or medical history were included and records were previously re-coded to maintain anonymity, in accordance with the principles of Good Clinical Practice and the Declaration of Helsinki. This research did not involve human participants and there was no access to identifying information; in this context, the Spanish legislation does not require patient consent and ethics committee approvalCitation14.
Study variables
The parameters obtained from the database included: patients’ age, date of admission, type of admission, date of discharge, type of discharge, readmission rate (defined as subsequent readmission for the same cause within 30-days after discharge), primary diagnosis, up to 20 secondary diagnoses registered during the admission, medical procedures and total admission medical cost.
Data analysis
Patients with septic arthritis were identified by the primary diagnosis code. Patients’ were grouped into the adult population and the pediatric population. Data obtained from the first admission registered per patient was used to evaluate patient characteristics, while the analysis of medical costs and admission details included all admission files.
The mortality rate was calculated within hospital settings as the annual number of deaths within all patients registered in the National discharge database with a case of septic arthritis. Medical costs were obtained from the database, where they are assigned to each admission file according to the standardized average expenses of admissions and medical procedures determined by the Spanish Ministry of Health (costs of medical examination, medication, surgery, diet, costs associated with personnel, medical equipment and resources). All medical costs were adjusted for inflation to 2019 values.
The Kolmogorov-Smirnov test was used to test for normality. Frequencies and percentages are reported for dichotomous variables and mean or median and 95% confidence interval (CI) were calculated for continuous variables. Two-tailed non-parametric independent t-test (Mann-Whitney U test) or one-way analysis of variance (Kruskal-Wallis test) were used as appropriate. A p < .05 is considered statistically significant.
Microsoft Excel© Professional Plus 2016 (Microsoft Corporation, Redmond, WA, USA) and StataSE 12 for Windows (StataCorp LP. 2011. Stata Statistical Software: Release 12. College Station, TX, USA) were used to perform statistical analysis.
Results
Inclusion criteria claimed files corresponding to 16,438 individual patients. The median age was 56 years; 62.8% of the patients were males (). The knee was the most commonly involved joint, registered in 49% of the cases, 19% of the cases were in the arm, hand or shoulder, 12% in the pelvic region and 9% in the ankle or foot. The microorganism was not always specified; 25.6% of the files specified a staphylococcus infection and 8.0% specified a streptococcus infection, only 2.7% of admissions described an antibiotic-resistant infection. A number of secondary diagnoses were registered in the database; the most frequently diagnosed conditions were hypercholesterolemia, diabetes mellitus and essential hypertension, which were more common in adult patients.
Table 1. Summary of patient characteristics and comorbidities.
The majority of admissions (89.6%) were urgent or non-scheduled admissions and the median length of stay was 12 days (). Only 0.4% of the files corresponded to outpatient visits. Time of hospital stay increased significantly in adult patients versus pediatric patients. In 4.5% of hospital admissions, an ICU admission was registered, the median length of ICU stay was 3 days. In half of the cases (50.1%), follow-up was not required and in 12.2% follow-up was required in hospital settings; 11.8% of patients required readmission in the 30 days after discharge. The hospital mortality rate was 2.8%, median age of deceased patients was 81 years (95% CI 79–82). No deaths were registered in pediatric patients over the study period.
Table 2. Admission details and most frequent surgical and medical procedures registered during the admission (>10% of admissions).
The most frequent medical procedures registered during the admission were the injection of antibiotics (48.6%), diagnostic ultrasounds (34.8%), arthrocentesis (32.1%) and other exploratory and surgical interventions. Significant differences were found in the procedures registered between the pediatric and the adult population.
The median admission cost was €6,382 per patient over the study period (). No significant differences appeared between pediatric and adult patients or between different pathogens, however, admissions in which an arthrotomy was registered had a significantly lower cost than admissions without an arthrotomy registered in all age groups (p < .0001). Median admission cost increased significantly with the length of stay (p < .0001). The total annual cost was 12.7 million euros, considering all patients in the database.
Table 3. Mean annual direct medical cost in hospital settings.
Discussion
This study aimed to fill the existing gap in the literature on the economic burden of septic arthritis by reviewing individual hospitalization data from patients admitted with septic arthritis in Spanish hospitals over a ten-year period. The majority of patients identified in the study were adult patients, with a median age of 56 years; the median age of the pediatric population was 2 years. Similarly, a previous study in children with septic arthritis in a Spanish hospital described a population with 94% of patients under 2 years of ageCitation15. The same study found Staphylococcus aureus to be the most common pathogen, followed by Streptococcus agalactiaeCitation15. In line with previous evaluations, Staphylococcus aureus infections were the most frequent in the present study, both in the pediatric and the adult populationCitation1,Citation16. Antibiotic resistances were found in 2.7% of the admissions and were more frequent in adult patients, yet, these infections were not specified methicillin-resistant Staphylococcus aureus (MRSA).
In terms of comorbidity, adult patients registered a number of conditions that were uncommon in the pediatric population. The most frequent secondary diagnoses registered upon admission were hypercholesterolemia, diabetes mellitus and essential hypertension. A similar comorbidity profile has been previously described in adults with septic arthritis and must be considered in terms of prognosis and possible complicationsCitation17.
The majority of hospital admissions registered in the database corresponded to urgent admissions (89.6%), with a median length of stay of 12 days. Length of stay was shortened in pediatric patients although these registered more frequent ICU admissions. Longer hospitalizations have been previously registered in children with septic arthritis, with an average hospital stay of 13.5 days in Spain between 2008 and 2012 or 15.3 days in SingaporeCitation18,Citation19.
Fifty per cent of the patients required a follow-up in hospital settings, while any follow-up by general practitioners was not registered. The in-hospital mortality rate was 3.7% for adults in this study, while no deaths were registered in children. Comparably, previous evaluations have described short-term mortality between 3 and 11%, increasing when patients were followed for 90 days to 1 yearCitation7,Citation20–22.
The management of septic arthritis could not be thoroughly evaluated from data in this database due to the limited codes used to register medical and surgical procedures; e.g. the injection or infusion of antibiotics and the rate of arthrotomy appeared underrepresented in the database. Other procedures registered were diagnostic ultrasound, and other diagnostic imaging procedures, arthrocentesis, the local excision or destruction of lesions and arthroscopy. A previous study evaluating the management of septic arthritis in children in Spain was able to report the use of intravenous antibiotics and arthrotomy to treat these patients, however, similar data could not be obtained hereinCitation18.
Limited data is available in the literature on the medical costs of septic arthritis. The present study found a median admission cost of €6,382 per patient over the study period, with a total annual cost of 12.7 million euros. A previous study based in the United States estimated a median cost per hospital admission of €32,881 (US$37,563), with total charges reaching the €584,114,053 (US$667,295,812) in 2012 and in patients with septic arthritis as the primary diagnosis; however, the significant differences in the healthcare system and population must be consideredCitation23. Length of hospital stay was determinant of total admission cost. Interestingly, no significant differences were found between pediatric and adult patients.
A number of limitations may have influenced the results obtained. Patient inclusion was based on the primary diagnosis registered in the database; yet, microbiological confirmation was not always available. Other limitations derived from data codification must be considered, including the under-registration of medical and surgical procedures including antibiotics and arthrotomy; nevertheless, admission costs were not directly associated with these codes which ensures the reliability of economic data.
Conclusions
This study provides novel data on the medical costs of septic arthritis in Spain, groundwork for a future revision of resource allocation decisions aiming to reduce the burden of this condition at the healthcare system level. To date, few studies have explored the economic burden that septic arthritis poses for healthcare systems, which could increase in the upcoming years. Further research will be required to quantify the total medical and societal burden associated to this condition.
Transparency
Declaration of funding
This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.
Declaration of financial and other interest
The authors declare that they have no competing interests. A reviewer on this manuscript has disclosed that they are a consultant for DePuy Synthes, ConvaTec, Publication Royalties from SLACK, Inc. and Johns Hopkins University Press as well as an Editorial Board member for Journal of Arthroplasty and a committee member for American Academy of Orthopaedic Surgeons. They have no conflicts that are relevant to this review. The other peer reviewers on this manuscript have no other relevant financial relationships or otherwise to disclose.
Author contributions
JD contributed to the investigation by analyzing and interpreting the burden associated to septic arthritis in Spain and was a major contribution in the intellectual content revision. AM analyzed the current situation of septic arthritis in Spain, interpreted the statistical data and was a major contributor in writing the manuscript. All authors read and approved the final manuscript.
Ethics approval and consent to participate
Ethics committee approval and consent were not required for this study.
Data availability statement
Data sharing is restricted due to legal stipulations, yet the data that support the findings of this study is fully available from the Spanish Ministry of Health via the Unit of Health Care Information and Statistics (Spanish Institute of Health Information) for researchers who meet the criteria for access to confidential data at: https://www.mscbs.gob.es/estadEstudios/sanidadDatos/home.htm.
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