Retrospective Cohort Study to Determine the Effect of Socioeconomic Status and Distance to Hospital on Negative Appendicectomy Rates in a Rural Setting
Funding: The authors received no specific funding for this work.
ABSTRACT
Background
The impact of socioeconomic status and distance to hospital on negative appendicectomy rates is unknown. These factors have been shown to be important predictors of health in a rural setting.
Objective
To determine whether socioeconomic status and road distance to hospital were risk factors for negative appendicectomy.
Methods
A retrospective analysis of all appendicectomies at a large rural hospital in Australia between January 2018 and December 2022 was performed. Patients' data were extracted from electronic medical records. Regression modelling was performed to determine whether socioeconomic status and road distance to hospital were risk factors for negative appendicectomy. The surgical outcomes for negative and positive appendicectomies were compared.
Results
A total of 830 patients were included in our analysis, of which 106 (12.8%) had negative appendicectomy. The rate of negative appendicectomy was not significantly impacted by socioeconomic status (OR = 1.004, 95% CI 0.989–1.20, p = 0.583) or road distance to hospital (OR = 1, 95% CI 0.998–1.001, p = 0.635). There was no significant difference in complications and 30-day readmission rates between patients in the negative and positive appendicectomy groups.
Conclusions
In a rural setting, the risk of negative appendicectomy does not increase with lower socioeconomic status and longer road distance to hospital. This challenges the prevailing notion that rural surgeons have a lower threshold to operate on patients with lower socioeconomic status or who live further away from hospitals due to the perception that these patients have less access to healthcare.
Summary
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What is already known on this subject?
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Negative appendicectomy is a consequence of misdiagnosing appendicitis. It predisposes patients to unnecessary risks associated with surgery and poses significant healthcare costs.
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Clinical, biochemical and radiologic risk factors for negative appendicectomy are well known. They include female sex and normal WCC/CRP. The use of imaging has been proven to reduce the rate of negative appendicectomies.
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The impact of social risk factors on negative appendicectomy rates such as socioeconomic status and distance to hospital is unclear. These factors are particularly important in a rural healthcare setting.
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What this study adds?
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This study demonstrates that socioeconomic status and distance from hospital do not impact negative appendicectomy rates in a rural setting.
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1 Introduction
Acute appendicitis is a clinical diagnosis, supported by radiological and laboratory results [1]. Negative appendicectomy is a consequence of misdiagnosing appendicitis and raises several concerns. Firstly, patients undergoing unnecessary surgery are exposed to the risk of anaesthetic, intraoperative and postoperative complications [2]. Trust in the healthcare system may erode, affecting long-term health behaviours such as adherence to medications and follow-up for chronic diseases. Furthermore, the misdiagnosis of appendicitis can delay identification and treatment of the actual pathology [3]. There is also a significant healthcare cost related to unnecessary surgery, exacerbated by the longer inpatient stays and further investigations that may be seen with negative appendicectomy [4].
Rates of negative appendicectomy have been recorded as high as 35% [5]. Known risk factors for negative appendicectomy include female sex, normal white cell count, normal C-reactive protein levels and normal total serum bilirubin levels [6-8]. The use of ultrasound and CT imaging has been shown to reduce the rates of negative appendicectomy [9, 10]. While clinical, biochemical and radiological risk factors of negative appendicectomy are well described in the literature, social risk factors such as socioeconomic status and road distance to hospital are less well understood. In a rural setting, these factors may influence the surgical decision-making regarding whether to proceed with a diagnostic laparoscopy when the diagnosis of appendicitis is equivocal or uncertain.
Current guidelines recommend an individualised approach to the diagnosis of appendicitis [1, 11]. While imaging may be useful, it is not readily available in all healthcare settings and may be nondiagnostic [12]. Moreover, the use of CT routinely prior to surgery is not recommended in certain populations such as young individuals or pregnant women with possible appendicitis [1, 13]. Proceeding with a diagnostic laparoscopy in the setting of an unclear diagnosis has been justified as a preventative measure against perforated appendicitis [13, 14]. It is accepted that the morbidity associated with a negative appendicectomy does not outweigh the risk of a perforated appendicitis [15]. Surgeons must consider multiple factors when deciding whether to proceed with surgery. Patient history and examination, along with blood tests, are used as indicators to determine the appropriateness of surgery. Less commonly discussed but also clinically relevant are the patient's social circumstances, which may influence a surgeon's decision on whether to proceed with surgery.
Socioeconomic status and distance from hospital are two social factors that may have an impact on negative appendicectomy rates [16, 17]. Patients with low socioeconomic status have reduced access to healthcare and poorer health literacy compared to the general population. They may be less likely to seek medical attention due to financial constraints and are also more likely to live further away from health infrastructures such as hospitals or medical clinics [18]. Increased distance from hospital results in poorer physical accessibility to health services such as surgery [19]. These factors may prompt surgeons to have a lower threshold to proceed with surgery in patients with lower socioeconomic status or who live further away from hospitals, to mitigate their risk of perforated appendicitis [12, 20]. The unintended consequence of this is higher rates of negative appendicectomies in these populations.
The primary aim of this study was to determine whether socioeconomic status and road distance to hospital were risk factors for negative appendicectomy at a large rural hospital. Our hypothesis was that patients with lower socioeconomic status or those who resided further from hospital were at a higher risk of having a negative appendicectomy compared with the general population.
2 Methods
2.1 Study Design and Setting
This was a retrospective cohort study of sequential patients undergoing appendicectomy between January 2018 and December 2022 at a rural referral hospital that serves a population of 279 422 and encompasses an area of 247 000 km2. Patients presenting to this hospital either live locally or are transferred from smaller peripheral hospitals that are staffed by nonsurgical doctors or nurse practitioners. Local patients will present either directly to the emergency department or be referred by their primary care physician. Transfer from peripheral centres occurs through three pathways: [1] self-arranged transportation, [2] ambulance transportation or [3] aeromedical transportation. The hospital has a 24-h on-call general surgery service with full access to operating theatres that facilitates expedited assessment and management of emergency presentations. There are 160 acute inpatient beds and an intensive care unit that can provide support for patients of all ages with appendicitis. Unwell patients requiring care beyond the hospital's resources can be transferred to better-resourced metropolitan tertiary centres. This retrospective study was approved by the Human Research Ethics Committee at our institution and was assigned as low and negligible risk research.
2.2 Data Collection
Consecutive patients of all ages who underwent an appendicectomy between January 2018 and December 2022 were identified using our hospital's electronic medical databases. The patients were screened against our exclusion criteria to determine if they could be included in our analysis. Baseline demographic information, residential postcodes, time from presentation to surgery, duration of surgery, operative approach, intraoperative findings, histopathologic findings, length of stay, postoperative complications and 30-day readmission rates were extracted from the patients' medical records. The collected data were stored in a secured electronic database with two-layer security in accordance with our ethics submission.
2.3 Exclusion Criteria
Patients who received an interval appendicectomy or had their appendix removed in another primary but unrelated procedure were excluded. Patients whose address did not fall within the catchment area of our hospital were also excluded, as many of these patients are visitors and can distort our results in relation to road distance to hospital. Prisoners and pregnant women were excluded.
2.4 Socioeconomic Status
Patients' residential postcodes were used to determine their socioeconomic status using the Australian Bureau of Statistics' Socio-Economic Indexes for Areas 2016 data (SEIFA 2016) [21]. This publicly available database produces several indexes reflective of socioeconomic status based on multiple factors such as income level, educational attainment, employment, housing and disability. The Index of Relative Socioeconomic Advantage and Disadvantage (IRSAD) was used in this study and considers both advantages and disadvantages within a postal area to determine socioeconomic status. Patients' IRSAD scores were converted to percentiles and categorised into quartiles from 1 (lowest SES) to 4 (highest SES).
2.5 Distance to Hospital
Distance to hospital was determined using patients' residential postcodes. Google Maps was used to determine the road distance between the centre of the patients' postcode and the hospital. This method has been used in multiple previous research publications of a similar nature [22-24]. We specifically chose not to use the patients' exact address to determine distance to hospital because this does not accurately reflect the general area where most daily activities (e.g., shopping, schooling) take place. Additionally, most transferred patients arrived from a peripheral hospital rather than from their exact address. Peripheral hospitals are strategically placed at town centres, so measuring road distance to hospital from the centre of residential postcode may be more accurate than using exact addresses.
2.6 Indigenous Background
Our hospital caters to a large Indigenous Australian population. Upon presentation to hospital, patients can self-report whether they are from an Aboriginal or Torres Strait Islander background. This information allows the state government to assess the impact of healthcare services in the community and monitor changes in health and well-being over time [25].
2.7 Outcomes
The primary outcome was to determine whether there was an association between socioeconomic status and road distance to hospital with negative appendicectomy. A negative appendicectomy was defined as an appendicectomy that demonstrated no intraoperative or histopathologic evidence of appendicitis as per AAST guidelines [26]. The secondary outcome was to determine whether there was any difference in time to theatre, duration of surgery, operative approach or postoperative complications between patients who underwent negative and positive appendicectomies.
2.8 Statistical Analysis
Statistical analysis was performed using IBM SPSS 28.0 (IBM Corp, Chicago, IL, USA). Baseline characteristics were analysed using descriptive statistics. The Shapiro–Wilk test was used to assess normality. Missing data points were accounted for using pairwise deletion. Continuous variables were compared using the Mann–Whitney U test, and categorical variables were compared using either the Chi-squared test or Fisher's exact test. Regression modelling was used to determine the association between variables and negative appendicectomy. A two-sided p-value < 0.05 was considered statistically significant.
3 Results
Between January 2018 and December 2022, a total of 901 patients underwent appendicectomy, of whom 830 met our inclusion criteria. Of these patients, 106 (12.8%) had a negative appendicectomy. Table 1 compares the baseline characteristics of patients who had a negative appendicectomy with those who had a positive appendicectomy.
| Negative appendicectomy, n = 106 | Positive appendicectomy, n = 724 | p | |
|---|---|---|---|
| Age, years, median (IQR) | 18 (14) | 27 (25) | < 0.001 |
| Sex, n (%) | < 0.001 | ||
| Male | 27 (25.5) | 404 (55.8) | |
| Female | 79 (74.5) | 320 (44.2) | |
| Socioeconomic status, n (%) | 0.905 | ||
| Quartile 1 (most disadvantaged) | 34 (32.1) | 267 (36.9) | |
| Quartile 2 | 69 (65.1) | 426 (58.8) | |
| Quartile 3 | 3 (2.8) | 31 (4.3) | |
| Quartile 4 (most advantaged) | 0 (0) | 0 (0) | |
| Distance from hospital, km, median (IQR) | 61.3 (142.1) | 61.3 (131.6) | 0.784 |
| Indigenous status, n (%) | < 0.023 | ||
| Indigenous | 37 (34.9) | 174 (24) | |
| Non-Indigenous | 69 (65.1) | 550 (76) |
3.1 Age and Sex
The median age of patients who had a negative appendicectomy was significantly younger than those who had a positive appendicectomy (p < 0.001). The proportion of patients who were female was higher in the negative appendicectomy group than in the positive appendicectomy group (74.5% vs. 44.2%, p < 0.001). On binary logistic regression, female sex was a significant risk factor for negative appendicectomy (OR = 3.694, 95% CI 2.330–5.857, p < 0.001).
3.2 Socioeconomic Status
The socioeconomic status of patients undergoing negative appendicectomy and positive appendicectomy was similar (p = 0.905). The majority of patients in both groups were in the second socioeconomic quartile, followed by the first quartile, and then the third quartile. No patients were in the most advantaged socioeconomic quartile. On binary logistic regression, there was no association between socioeconomic status and negative appendicectomy (OR = 1.004, 95% CI 0.989–1.20, p = 0.583).
3.3 Road Distance to Hospital
The median road distance to hospital between patients who had a negative appendicectomy and those who had a positive appendicectomy was comparable [61.3 (IQR 142.1) vs. 61.3 (IQR 131.6) km, p = 0.784]. On binary logistic regression, there was no association between road distance to hospital and negative appendicectomy (OR = 1, 95% CI 0.998–1.001, p = 0.635).
3.4 Indigenous Background
The proportion of Indigenous patients who had a negative appendicectomy (17.5%) was higher than the proportion of non-Indigenous patients who had a negative appendicectomy (11.1%). On binary logistic regression, Indigenous background was a risk factor for negative appendicectomy (OR = 1.695, 95% CI 1.098–2.617, p = 0.017).
3.5 Preoperative Laboratory Test
Table 2 outlines the preoperative laboratory tests and imaging of patients who underwent appendicectomy. Patients in the positive appendicectomy group had a higher median white cell count (p < 0.001), neutrophil count (p < 0.0001) and C-reactive protein level (p < 0.001) than those in the negative appendicectomy group. On binary logistic regression, the risk of negative appendicectomy declined with a white cell count > 11 × 109/L (OR = 0.175, 95% CI 0.111–0.277, p < 0.001), neutrophil-to-white cell count ratio ≥ 75% (OR = 0.209, 95% CI 0.131–0.332, p < 0.001) and C-reactive protein level > 5 mg/L (OR = 0.247, 95% CI 0.155–0.395, p < 0.001).
| Negative appendicectomy, n = 106 | Positive appendicectomy, n = 724 | p | |
|---|---|---|---|
| Laboratory findings | |||
| White cell count, median (IQR) | 9.6 (3.7) | 13 (5.8) | < 0.001 |
| Neutrophils, median (IQR) | 6.15 (3.9) | 10.2 (5.8) | < 0.001 |
| C-reactive protein, median (IQR) | 4 (17) | 20 (55.75) | < 0.001 |
| Imaging findings | |||
| Ultrasound, n (%) | < 0.001 | ||
| Positive | 12 (11.3) | 108 (14.9) | |
| Negative | 37 (35) | 95 (13.1) | |
| Equivocal | 17 (16) | 47 (6.5) | |
| Not performed | 40 (37.7) | 474 (65.5) | |
| Computed tomography, n (%) | < 0.001 | ||
| Positive | 12 (11.3) | 344 (47.5) | |
| Negative | 8 (7.5) | 7 (0.9) | |
| Equivocal | 4 (3.8) | 19 (2.6) | |
| Not performed | 82 (77.4) | 354 (48.9) | |
3.6 Operative and Postoperative Details
Table 3 compares the operative and postoperative details of patients in the negative and positive appendicectomy groups. The time to theatre from admission was higher in the negative appendicectomy group than in the positive appendicectomy group, but this was not statistically significant (p = 0.059). The duration of surgery was significantly higher in the positive appendicectomy group than in the negative appendicectomy group (p < 0.001). There was no significant difference in rates of laparoscopic versus open surgery between the two groups (p = 0.435). A greater conversion rate from laparoscopic to open surgery was seen in the positive appendicectomy group, but this was not statistically significant (p = 0.061).
| Negative appendicectomy, n = 106 | Positive appendicectomy, n = 724 | p | |
|---|---|---|---|
| Operation | |||
| Time to theatre, minutes, median (IQR) | 275 (588) | 191.5 (467.3) | 0.059 |
| Duration of surgery, minutes, median (IQR) | 79 (29.8) | 87 (32) | < 0.001 |
| Approach to surgery, n (%) | 0.435 | ||
| Laparoscopic | 100 (94.3) | 695 (96) | |
| Open | 6 (5.7) | 29 (4) | |
| Conversion to open (%) | 0 (0) | 23 (3.3) | 0.061 |
| Postoperative course and complications | |||
| Length of stay, days, median (IQR) | 2 (1) | 2 (1) | 0.457 |
| Wound infection | 2 (1.9) | 18 (2.5) | 0.707 |
| Ileus | 0 (0) | 4 (0.6) | 0.246 |
| Pneumonia | 0 (0) | 16 (2.2) | 0.443 |
| Urinary retention | 0 (0) | 3 (0.4) | 0.507 |
| Readmission within 30 days | 0 (0) | 15 (2.1) | 0.457 |
| Reoperation | 6 (5.7) | 31 (4.3) | 0.239 |
| Transfer to tertiary hospital | 0 (0) | 4 (0.6) | 0.496 |
Length of stay was comparable between the negative and positive appendicectomy groups (p = 0.457). There were no significant differences between the two groups in terms of postoperative complications such as wound infection (p = 0.707), postoperative ileus (p = 0.246), pneumonia (p = 0.443) and urinary retention (p = 0.507). There were similar 30-day readmission rates (p = 0.457) and reoperation rates (p = 0.239) between the two groups. Four (0.6%) patients in the positive appendicectomy group needed to be transferred to a tertiary centre for more specialised care, whilst no patients in the negative appendicectomy group were transferred (p = 0.496).
4 Discussion
Our study demonstrated a negative appendicectomy rate of 12.8%, which was significantly lower than the national average in Australia of 19% based on the largest prospective multicentred study [27]. We demonstrated that socioeconomic status and road distance to hospital did not affect the rate of negative appendicectomy in a rural setting. Our study also revealed that Indigenous Australians had an increased risk of negative appendicectomy compared to the general population, but the reason for this is unclear and needs further study.
A commonly perceived notion is that patients with low socioeconomic status are less likely to remain in hospital for monitoring or present if their symptoms re-emerge, potentially because of the cost associated with medical care and lost income from work absence [28]. Surgeons may, therefore, have a lower threshold to operate on these patients to reduce their risk of complicated appendicitis. However, this notion was not supported by our study. All the included patients in our study were in the lowest three socioeconomic quartiles, which is reflective of the general demography of rural Australia. The finding that there was no significant difference in negative appendicectomy rates between patients in lower and higher socioeconomic groups challenged our hypothesis. It also contests the prevailing dogma that low socioeconomic status negatively impacts the diagnosis and treatment of appendicitis [29].
One explanation for why socioeconomic status did not appear to have any effect on the rate of negative appendicectomy may be Australia's universal healthcare system. This allows patients to be admitted and treated without any out-of-pocket costs [30]. Patients are, therefore, more willing to stay in hospital for monitoring and have less reluctance to represent if their symptoms re-emerged after discharge. Thus, surgeons are not affected by their patient's financial status when deciding on whether to proceed with surgery or not. In addition, Australians are entitled to a minimum period of paid sick leave annually. This minimises the impact of work absence due to hospital admission on patients' personal income.
Road distance to hospital did not affect rates of negative appendicectomy. Our initial assumption that surgeons would have a lower threshold to operate on geographically distant patients due to the logistical challenge of future access to surgical services was not reflected in our results. One reason for this may be because our hospital has multiple peripheral sites that can provide nonoperative treatment for appendicitis prior to transfer to our hospital for appendicectomy. This has been shown to reduce the risk of complicated appendicitis. Indeed, previous studies have demonstrated that road distance to hospital did not increase the likelihood of perforated appendicitis [24]. Consequently, surgeons at our rural hospital are not pressured to perform an appendicectomy for rural patients with equivocal appendicitis.
Another possible explanation is that the time taken for a patient to transfer from a peripheral site to our hospital may allow the diagnosis to declare itself. Surgeons at our hospital are therefore able to make better clinical decisions on whether to proceed with surgery based on symptoms that improved or worsened during transfer. Peripheral sites are also staffed by clinicians and nurses who are experienced at triaging patients with a low clinical probability of appendicitis. These patients are, therefore, not transferred to our hospital and do not undergo laparoscopy, reducing the rate of negative appendicectomy.
Our study incidentally revealed that Indigenous patients had a higher risk of negative appendicectomy compared to their non-Indigenous counterparts. It is unclear why this may be the case, and this will need to be further investigated in future research before conclusions can be drawn. It is important to recognise that this study is retrospective, and the results may not necessarily translate to real-life clinical significance. Indigenous Australians are known to experience significant health inequities compared to non-Indigenous Australians [31, 32]. We suspect that multiple factors, including social and cultural reasons, may underpin the reason behind this disparity in negative appendicectomy between Indigenous and non-Indigenous Australians. Unfortunately, we are limited by the scope of our ethics for this paper to explore this in further detail.
In concurrence with existing studies, we demonstrated that white cell count > 11 × 109/L, neutrophil-to-white cell count ratio ≥ 75% and C-reactive protein level > 5 mg/L were associated with a reduced risk of negative appendicectomy. Female sex and younger age were associated with a higher risk of negative appendicectomy, and this may be due to the reluctance of surgeons to perform preoperative CT on these patients due to radiation risks.
The increased use of imaging such as ultrasound and computed tomography has seen a dramatic decline in negative appendicectomy rates [9, 10]. Some surgeons have reasoned that a higher negative appendicectomy rate is no longer acceptable in this imaging era as it predisposes the patient to complications related to unnecessary surgery [33]. However, our study demonstrated that complication rates related to negative appendicectomy are low. This suggests that negative appendicectomy can be performed safely and still has a role in surgical practice, particularly in unwell patients where the diagnosis remains unclear or in a resource-limited rural setting where imaging is not always available.
Limitations of our study include the fact that our data were collected retrospectively and may be prone to recording error. We also could not collect information related to the patients' prehospital clinical course and treatment as these were recorded on external databases such as peripheral hospitals or private general practice clinics. Our ethics approval also limits our ability to explore the reason behind the incidental finding that Indigenous Australians have a higher risk of negative appendicectomy compared to the general population. Furthermore, our data related to socioeconomic status were based on the 2016 census so may be outdated; however, these were the latest published figures at the time of research. Finally, this study was carried out at a single rural hospital, which limits its applicability to other hospitals. We encourage other surgeons to carry out similar studies with a broader range of ethics submissions to see if our findings can be replicated in other health districts.
5 Conclusion
In a rural setting, patients with lower socioeconomic status and increased road distance to hospital did not have increased rates of negative appendicectomy. These social factors did not appear to lower surgeons' thresholds in proceeding with surgery in a patient with an equivocal or uncertain diagnosis of appendicitis. Future research comparing our outcomes with other rural areas and larger metropolitan centres will provide a more comprehensive assessment of the factors influencing negative appendicectomy.
Author Contributions
Roy Huynh: conceptualisation, data curation, formal analysis, investigation, methodology, project administration, software, resources, validation, writing – original draft, writing – review and editing. Kevin Tree: conceptualisation, data curation, investigation, methodology, writing – review and editing. Matthew Smith: conceptualisation, data curation, investigation, methodology, writing – review and editing. Lily Builth-Snoad: conceptualisation, data curation, investigation, methodology, writing – review and editing. Faisal Syed: conceptualisation, data curation, investigation, methodology, writing – review and editing. Dean Fisher: conceptualization, investigation, methodology, software resources, supervision, writing – review and editing.
Ethics Statement
This retrospective study was approved by the Greater Western Human Research Ethics Committee and was assigned as low and negligible risk research. The Human Research Ethics Application number is 2022/STE03897.
Consent
The authors have nothing to report.
Acknowledgement
Open access publishing facilitated by University of New South Wales, as part of the Wiley - University of New South Wales agreement via the Council of Australian University Librarians.
Conflicts of Interest
The authors declare no conflicts of interest.
Open Research
Data Availability Statement
The data that support the findings of this study are available from the corresponding author upon reasonable request.
