Research on hospitalization costs of inguinal hernia surgery performed at county-level public hospitals in Anhui, China: Insights into Influencing Factors

Background: Lancet gave a 99-point high score to the comprehensive level of diagnosis and treatment of inguinal hernia in China, and more than half of the inguinal hernia surgery procedures were completed in primary hospitals. At present, the hospitalization costs of inguinal hernia surgery patients in primary hospitals, the influencing factors, and the path between the factors are unclear. Innovative methods are needed to quantify the research and evaluation of hospitalization costs for inguinal hernia surgery patients to emphasise the impact of relevant measures on surgeons and hospital cost-control mechanisms. Methods: A retrospective method was used to collect data from inguinal hernia surgery patients. The relationships between hospitalization costs and the following factors (age, gender, surgery, surgical method, surgical time, preoperative bed stay, postoperative bed stay, length of stay, and surgical costs) were analyzed using Spearman’s correlation analyzes, and how these factors influenced hospital expenditure was explored through structural equation modelling. Results: According to Spearman’s rank correlation analysis, the hospitalization costs were related to the eight selected indicators (rs = -0.084 - 0.549, p < 0.01), and the surgical time was most relevant. The total effect of the surgical time on the hospitalization costs (total effect = 0.459) ranked first in the structural equation model, which means that the risk of hospitalization costs was higher with a longer surgical time.The choice of surgical method had a Study All authors. Study design: First authors. Data acquisition: Quality control of data and algorithms: Data analysis and Statistical


Introduction
Surgical conditions represent an enormous but unrecognized source of disease burden globally. Research has indicated that 11% of the world's disability adjusted life years (DALYs) result from surgical conditions likely to require [1] . Surgical treatment allows patients to regain functional status and engage in productive activity, but produces a certain economic burden for patients [2] . Although efforts are being undertaken worldwide to control medical expenses and alleviate pressure on patients' finances, policies and facilities leave a large gap between the provision of health services and public demand in a resource-poor environment, and "high treatment costs" remain severe. Innovative methods to quantify the medical costs of surgical treatment are needed to guide programmatic intervention and to inform advocacy efforts.
Inguinal hernia is one of the most common surgical procedures. More than 20 million patients undergo groin hernia repair annually worldwide [3] . In this study, we attempt to systematically explain the disease from the aspects of preclinical medicine, local anatomy, and clinical medicine [4,5] . Inguinal hernia has become an important branch of surgery. Mock et al. defined inguinal hernia as a "priority 1 surgical condition" because it represents a significant global public health burden that can be treated with a simple, cost-effective surgical procedure [6] .
In addition, selective inguinal hernia repair (IHR) can prevent rare but serious and expensive complications, including strangulation, intestinal obstruction, and death [7,8] . Surgery is considered the most cost-effective way to treat inguinal hernia over the long term [9] .
It is estimated that the present cost of repairing all symptomatic inguinal hernias in Ghana is US$53 million, whereas US$103 million will be required to eliminate hernias over the next 10 years [10] . Seung-Rim reported that the costs of IHR in Korea gradually increased from $1,000 to $1,600, and a dramatic increase was observed in the use of laparoscopic inguinal hernia repair, from less than 3% in 2007 to approximately 30% in 2015 [11] . Inguinal hernia repairs in the US reached nearly 800,000 cases in 2003, and the repair of femoral hernias is estimated to cost US$3.2 billion annually [12,13] .
China is the most populous developing country in the world. Epidemiological studies over the past decade have shown that the annual incidence of inguinal hernia is 3.6‰-5.0‰, and the prevalence of inguinal hernia is as high as 1.16% in those over age 65 [14] . In 2017, The Lancet gave a 99-point high score to the diagnosis and treatment of inguinal hernia in China, ranking fourth in the world, due to lower costs and better results [15] . At present, more than 50% of inguinal hernia surgical procedures are completed in primary hospitals, but the costs and their influencing factors remain unclear. Research data on IHR expenditures come from institutional medical records. Therefore, medical expenses can be precisely tracked. The direct costs of inguinal hernia treatment include diagnosis, examination, consumables, and medicine, among others [16] . For inguinal hernia patients, the length of stay (LOS) [17] , surgical time [18] , and surgical method [19] all affect medical expenses. Therefore, it is crucial to gain a population-level view of the inguinal hernia expenditures from the perspective of sociodemographic characteristics and the distribution of treatment cost characteristics for health care decision-making. Considering the aforementioned literature, both surgery and LOS have demonstrated an association with hospitalization costs in inguinal hernia patients. However, there is limited information to explain the association between other contributing factors and hospitalization costs of inguinal hernia patients. Thus, we investigated the mediating effect of surgery and LOS on the association between these variables and hospitalization costs among patients with inguinal hernia surgery (IHS). We hypothesised that IHS would be associated with a high risk of hospitalization costs through prolonged LOS in the hospital. Moreover, the distribution of age and gender would be associated with surgery (e.g., method).
China is currently reforming its national health care system to establish a more equitable health system through a series of policies and interventions [20] . Assessing and describing traits of the costs of treatment in China is a necessary first step in achieving this goal. Therefore, analyzing the influencing factors of hospitalization costs in patients with IHS is essential.
Data calculated based on medical institutions' expenditures to analyze the factors that may affect IHR and their related relationships may help determine decisions related to clinical operations and hospital management measures to protect patients' rights and achieve the universal health care coverage strategy proposed by the WHO.

Data source and study design
China has a dual urban-rural structure. The primary medical and health service system is led by county-level public hospitals that serve the majority of the national population. When residents have medical needs, county-level public hospitals are their first choice [21] . Anhui Province is one of the first pilot provinces for medical and health reform in China. County-level public hospital reform has always been at the forefront in China [22] . We assessed the top 10 diseases by number of surgical procedures in Anhui's county-level public hospitals. Inguinal hernia surgery ranked first. In line with the International Classification of Diseases 10 th Revision (ICD -10), we collected the relevant data on inguinal hernia patients whose main diagnostic code was K40.

Quality control and data management
The investigators involved in data extraction underwent training and had a fixed set of data collection methods. Patient medical records in the hospital information system were electronically imported to another data terminal for on-site investigation. The investigators used tools to sort cases and identify missing or outliers and suspicious errors so that they could examine and evaluate the quality of the extracted data. We confirmed incomplete data with the original medical institution to ensure its accuracy and checked the patient information detail by detail, excluding outpatient and other non-surgical patient data. We ultimately obtained a total of 2,606 cases that were effectively analyzed.
We pre-processed the data after data collection. We selected the basic patient information

Statistical analysis
We conducted a descriptive analysis of the data, and the Shapiro-Wilk normality test of the main indicators was used at first. We found that the hospitalization costs, LOS, and surgical time did not obey the normal distribution, but the data showed a normal distribution after logarithmic conversion. In addition, the age was converted into categorical variable to analysis based on experience and literature [23] . The median and interquartile range of hospitalization costs in different categories were calculated and the difference in costs between the different groups in the same category was analyzed. Spearman's rank correlation test was used to examine the correlations between hospitalization costs, LOS, age, gender, surgical method, surgical time, preoperative bed stay, postoperative bed stay, and surgical costs. The structural equation model was used for path fitting. Continuous variables that did not obey the normal distribution were entered into the equation in logarithmic form to test the significance of the correlation between the variables and determine their direct and indirect effects.
The influencing factors and interrelationships of hospitalization costs of IHS patients were ultimately obtained.

Basic information on patients with IHS
We collected 1,121 patients in southern Anhui province and 1,485 patients in the north to participate in the survey, a total of 2,606 inpatients. Males accounted for 2,301 (88.3%) and females accounted for 305 (11.7%). Most of the inpatients (936, 35.9%) were over 65 years old.
Overall, 1,955 inpatients utilized open surgery (75.0%) and 651 (25.0%) adopted laparoscopic surgery. The surgical time of the majority of the inpatients (1175, 45.1%) ranged from 45 minutes to 90 minutes and the length of stay of 54.2% of the inpatients was generally less than or equal to 5 days. The median costs of each variable of expenditure were as follows: south were US$713.6 and north were US$622.6 (for region); males were US$646.1 and females were US$620.0 (for gender); the inpatients over 65 years old were US$684.2 (for age); open were US$629.3 and laparoscope were US$826.7 (for surgical method); ranges from 45 minutes to 90 minutes were US$665.9 (for surgical time); and within 5 days were US$604.0 (for length of stay). More information on these variables and the differences between them is presented in Table 1. Los ≤ 5 =1, 5 < Los ≤ 10 = 2, Los > 10 = 3.

Factors correlated with hospitalization costs
A correlation analysis was conducted to find the intercorrelations among the study variables.
The results of Spearman's rank correlations are shown in Table 2  Bootstrap (n = 2,000) method to recalculate all indicators [24] .The results of the SEM are displayed in Table 3, which shows that each fitting index reached the goodness-of-fit indices, and the model had a good fitting effect on each variable.

Analyzing the SEM results
The SEM variables were roughly divided into three cases according to the way they affected the total hospitalization cost. The first was the direct effect, such as surgical methods, surgical  Figure 1 and Table 4 and demonstrate the standardized path coefficients of the significant structural relationships among the tested variables (p < 0.05).

Discussion
Characterizing the hospitalization costs of patients with IHR is an important step in clarifying treatment-related factors, providing evidence-based evidence to key stakeholders, and rationalizing the utilization of patients' medical and health resources. This is not only the core territory of health economics, but also in line with the development trend of individualized treatment of patients with inguinal hernia. We found that the relationship between the selected study variables and hospitalization costs was siginifigant, including age, gender, surgical method, surgical time, preoperative bed stay, postoperative bed stay, length of stay, and surgical costs. Of note, these findings are consistent with other studies [17][18][19]25,26] . However, it has not been reported how the factors affect each other and the hospitalization costs by which method.
In our study, the proportion of men with IHS far exceeds that of women, which is similar to most studies [27,28] . We suspect that this may be related to the pathogenesis of inguinal hernia. It is more likely for men to suffer from increased abdominal pressure as a result of lifestyle habits such as smoking and higher workloads, making them more susceptible to diseases than women [29] . In therapy [30] . Although we divided the IHR into different groups, we found that the median hospitalization costs of the different groups were almost concentrated at approximately US$580--870. According to the disclosure of medical service information in the fourth quarter of 2018 in Anhui province, the cost of a single case of inguinal hernia was US$922.6, indicating that the effect of IHR cost control of county-level public hospitals was good [31] . Previous studies have shown that laparoscopic IHR has the advantages of less postoperative pain, faster recovery, and fewer LOS than open IHR [32,33] . We found that the surgical method had no statistical significance on preoperative bed stay (rs = 0.009, p > 0.05) and postoperative bed stay (rs = -0.02, p > 0.05) when we used the Spearman's rank correlation to conduct a factor correlation study. Papachristou and Mitselou also reported similar observations [34] . This may be related to the medical environment and medical management characteristics of the data collection agency. The functional positioning of county-level public hospitals is mainly to diagnose and treat common and frequently occurring diseases in China, so there is an excellent treatment technology and level for inguinal hernia. Laparoscopic surgery is not widely promoted at county-level medical institutions and the overall utilization rate is low at present , which may reduce the impact on LOS when analyzing large samples [35] . Based on the regression analysis of the structural equation model, we found that the use of laparoscopy had no effect on the length of surgery. This may have something to do with the way we processed the data, so we did not make a detailed distinction between unilateral and bilateral IHR. Laparoscopic surgery takes longer than unilateral open IHR because it takes time to establish the lung-peritoneal cavity, but not necessarily longer than bilateral hernia repair [34] .
The patients' age and gender had indirect effects on the hospitalization costs through the LOS; the indirect effects of the former were 0.033 (p < 0.01) and the latter were 0.069 (p < 0.01). We consider that the LOS will be longer and the hospitalization costs will be higher due to the higher prevalence, poorer health, longer recovery times, and greater need for medical resources in older patients. Men had lower LOS than women, which may be related to differences in physiological characteristics, disease tolerance, and prognosis of patients of different genders [36] .
Surgery is not only associated with increased costs, but also with the prolonged LOS [37,38] .
Our research results suggest that the LOS has a regulatory effect on the hospitalization costs of patients with IHS, indicating that the LOS plays a role in buffering the impact of various factors on the hospitalization costs. The LOS is often seen as a key indicator of medical resource consumption [39] . The longer the LOS, the more medical resources are consumed and the higher hospitalization costs. In other words, shortening the LOS is an effective way of reducing the hospitalization costs for patients with inguinal hernia. In our study, preoperative and postoperative stays were included as part of the LOS, and they also affect hospitalization costs negatively. It is suggested that unnecessary inspection items should be reduced and the hospital bed turnover rate should be accelerated to reduce the LOS while ensuring the quality of diagnosis and treatment. We recommend that hospitals consider rational use of clinical pathways and day surgery to establish standardized treatment models and procedures for inguinal hernia from a developmental perspective.
We found that the surgical time was the main factor affecting hospitalization costs (total effect = 0.459). The direct effect of surgical time on the hospitalization costs was 0.358, and the indirect effect was 0.10 through the LOS, both of which had a positive impact. This means that increased surgical time will cause a risk of prolonged LOS, which is similar to results found by Gupta et al. [18] . Furthermore, the direct effect of surgical time on hospitalization costs can be understood as a longer operation often means that the disease is more complicated and difficult, and doctors need to invest more mental and physical effort. To embody the value of doctors' labour, the surgical costs will increase, increasing the total cost. As confirmed in this study, there was a correlation between the surgical time and the surgical costs (path cofficient = 0.071, p < 0.01).
This also conforms to the pricing trends of medical services that are being reformed in China [40] .
The pricing of medical services in China should highlight the value of technical services of medical personnel in the future, taking into account the resource investment of doctors in providing medical services, which should include the workload. Hospitals should also pay attention to this point while carrying out the performance compensation reform of doctors.The importance of this discovery for doctors is that they should pay more attention to the effect of surgical time and control it reasonably to effectively avoid increased resource consumption caused by unnecessary operations when performing IHR.
Surgeons not only need to be proficient in their own skills, but also constantly learn and master new technology. They must meticulously evaluate and select procedures and techniques that they are capable of mastering, which will help improve practice and operations [41] .
Laparoscopic IHR is such a good example. We found that laparoscopic surgery required higher medical costs than laparotomy, which is undoubtedly related to the use of surgical equipment and patch materials (total effect = 0.291). The costs of laparoscopic surgery can be significantly reduced if minimal use of disposable instruments and avoidance of preperitoneal balloon and tacker for mesh fixation [42] . There have been many studies comparing hospitalization costs as part of prospective data collection, and the results show the risk of higher costs associated with laparoscopic surgery. However, a recent cost analysis report on laparoscopic IHR demonstrated that this method may be more cost-effective than open surgery in the long run [43] . County-level public hospitals and surgeons need to update surgical methods, such as laparoscopic IHR. It does not have a fixed cost and is usually not included in the "package pricing" transaction. Doctors can make a comprehensive comparison and use the most cost-effective choice with patients.
Although some studies have shown the role of certain factors in influencing the hospitalization cost of patients with IHS, there have been no studies using appropriate statistical models to verify the structural relationship. On this basis, we used a structural equation model to explore the specific degree of influence and interrelationship between variables to achieve a better interpretation effect.

Limitations
This study has some limitations. First, We did not consider the relationship between the details on medical expenses, diagnosis costs, and other specific medical and hospitalization costs.
The lack of information such as medical insurance type, disease severity, and outcome is also a formulating IHR cost standards. The purpose of this study is to provide suggestions for the gradual formation of scientific medical cost management methods and to promote county-level public hospital reform. It also provides a reference for saving health system expenses and quickly releasing the potential social benefits of patients.