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Comparison of the perforation rate for acute appendicitis between nationals and migrants in Taiwan, 1996–2001
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Original Research
Comparison of the perforation rate for acute appendicitis between nationals and migrants in Taiwan, 1996e2001 T-L. Liu a, J-H. Tsay b, Y-J. Chou a, N. Huang c,* a
Institute of Public Health, National Yang-Ming University, Taipei, Taiwan, ROC Department of Social Work, College of Social Science, National Taiwan University, Taipei, Taiwan, ROC c Institute of Hospital and Health Care Administration, National Yang-Ming University, No. 155, Sec. 2, Li-Nong St., Taipei 11221, Taiwan, ROC b
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Article history:
Objective: Immigrant populations have grown rapidly in recent years in many countries.
Received 3 October 2009
Immigrant-related healthcare issues have thus become more and more important. The aim
Received in revised form
of this study was to assess any possible disparity in access to care between migrants and
27 April 2010
nationals under the national health insurance (NHI) system in Taiwan.
Accepted 21 May 2010
Study design: Retrospective population-based observational study.
Available online 16 August 2010
Methods: National population-based data on patients aged 20 years in Taiwan under the NHI programme were studied. The frequency of use and expenditure on ambulatory care, inpatient
Keywords:
care and emergency care were analysed separately. Ruptured appendicitis was also analysed as
Access to care
an outcome indicator for access to care. Logistic regression and two-part models were applied.
Healthcare utilization
Results: Overall, migrants had a lower rate of healthcare utilization than nationals, and this
Appendicitis
gap remained consistent from 1996 to 2001. However, using ruptured appendicitis as the
Migrants
outcome indicator, no significant overall difference in access to care was found between
Taiwan
nationals and migrants under the NHI programme in Taiwan (odds ratio 1.01, 95% confidence interval 0.93w1.11). Conclusion: This study found that although migrants had a lower rate of healthcare utilization than nationals, their rate of adverse outcome was similar to nationals when they faced an acute, non-selective emergency condition such as appendicitis. The findings suggest that the use of more dimensional indicators may help to avoid possible misleading inferences on the variation in access to health care in Taiwan. ª 2010 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
Introduction Disparity in access to care is a critical public health concern.1 ‘Equity of accessibility comprises how systematic differences are in using health care services and what are the outcomes
among various groups and the barriers that cause these differences.’2 Therefore, in addition to general healthcare utilization, a number of researchers have used appendicitis as a distinct indicator of access to care when assessing disparities among disadvantaged subpopulations.3e9 Acute
* Corresponding author. Tel.: þ886 2 2826 7372; fax: þ886 2 2826 1002. E-mail address: [email protected] (N. Huang). 0033-3506/$ e see front matter ª 2010 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.puhe.2010.05.009
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appendicitis is commonly used as the model outcome because it is one of the most common clinical problems in surgery. Most research has focused on differences between races, such as between Black and White populations in the USA, or on different types of insurance within a population. Only a limited number of studies have targeted migrants. With globalization, migrant populations have grown rapidly in recent years and their health-related issues have become increasingly important. Healthcare access is one major factor. Many have speculated that there may be access barriers associated with such a life transition; these include immigration and settlement,10 language disadvantage,11 lack of acculturation,12 unfamiliarity or distrust of the healthcare system,13 and a lack of legal status.14 These barriers may cause migrants to have difficulty with timely access to appropriate health services when adapting to a new environment, which could put them in a vulnerable situation. Several studies have used healthcare utilization as an indicator that allows assessment of possible disparities in access to care. These studies found that migrants had lower healthcare utilization than nationals.15e17 However, the lower healthcare utilization observed among migrants does not necessarily mean that there are disparities in access barriers. It could mean that migrants are healthier than nationals, which is known as the ‘healthy immigrant effect’.18,19 Hence, when assessing possible disparities in access to care between migrants and nationals, one should also pay attention to their health outcomes. Although there is evidence showing that migrants have lower healthcare utilization in general than nationals, there is very limited empirical evidence on their emergency surgical outcomes. Three studies have investigated health outcomes; two of these studies compared foreign-born and native-born populations in the USA using the preventable hospitalization rate for different diagnostic diseases,20,21 and the other study compared migrants and non-migrants in Greece using ruptured appendicitis as the indicator.8 The two US studies found that migrants tend to have a lower preventable hospitalization rate than nationals, and the study in Greece found that migrants have a significantly worse rate for ruptured appendicitis than non-migrants. Hence, the present study tried to assess any disparities in healthcare utilization between nationals and migrants under the national health insurance (NHI) programme in Taiwan between 1996 and 2001. In this study, ruptured appendicitis was used as an outcome indicator for access to care. Taiwan is an interesting setting in which to study this important research question. Firstly, similar to many Asian countries, the number of migrants in Taiwan is increasing rapidly; migrants represented approximately 1.7% of the total population in 2001. Therefore, access to care among migrants is becoming a major concern. Secondly, the NHI programme in Taiwan provides comprehensive coverage to all citizens and also to legal migrants with employment or who have lived in Taiwan for more than 4 months, as well as the dependents of such persons. Hence, studying the enrollees of the NHI programme avoids the confounding effect of insurance status. Thirdly, the population-based NHI datasets enable the minimization of selection bias which occurs when using hospitalbased datasets. The aim was to determine if accessibility to
the healthcare system is significantly worse among migrants than among nationals. Overall, this study may help to improve understanding of whether disparities in access to care exist between migrants and nationals under a universal and comprehensive health insurance programme in an Asian society.
Methods Data sources and study population In order to meet the study objectives, HDATA was used to compare healthcare utilization between migrants and nationals. HDATA is an NHI meta-database, constructed and managed by the National Health Research Institute. It links the NHI sample files and the death certificates for a random sample of 200,000 NHI beneficiaries out of a population of 21,400,826 enrolees who had ever been enrolled between 1995 and 2000. It contains comprehensive enrolment and utilization information for this random sample, which includes identification number, gender, date of birth, months of enrolment, expenditure amounts and insurable wage. The NHI sample files have also been linked to death certificates in HDATA. Those people who died during each particular year and those with incomplete data were excluded to calculate healthcare utilization. The distribution of the sample by year is presented in Table 1. Due to the small number of cases of appendicitis in the HDATA sample, an alternative data source was used to investigate the second objective. Instead of using the sample files, the 1996e2001 NHI inpatient claims files, enrolment files, major diseases files and hospital registry were used to identify all cases of appendicitis. The NHI inpatient file provided information on gender, date of birth, dates of admission and discharge, medical diagnosis and treatment codes, expenditure amounts and hospital identifier. The NHI enrolment files provided the patients’ insurable wage, and the major diseases files helped to identify patients with a major disease, as well as the type of major disease. Furthermore, the NHI hospital files provided information on the certification level, ownership and patient volume of the admitting hospitals. The linkage of the datasets was carried out using encrypted personal identification numbers, hospital identifiers and dates of birth; these procedures followed the guidelines of the
Table 1 e Descriptive statistics of the population in assessing healthcare utilization under the national health insurance programme in Taiwan, 1996e2001. Total
1996 1997 1998 1999 2000 2001
119,742 122,618 126,048 129,073 131,362 133,603
Nationals
Migrants
n
%
n
%
117,812 120,206 122,853 125,324 127,111 130,770
98.39 98.03 97.47 97.10 96.76 97.88
1930 2412 3195 3749 4251 2833
1.61 1.97 2.53 2.90 3.24 2.12
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National Health Research Institute. From the populationbased inpatient file, it was possible to identify 95,193 patients with appendicitis by International Classification of Disease 9th Revision (ICD-9) code (540.0, 540.1 and 540.9) who were aged 20 years during the study period (1996e2001). To avoid misclassification, only those cases where the principal procedure was appendectomy or the drainage of an appendiceal abscess (ICD operation codes 47.0 and 47.2) were captured. After excluding patients whose gender was missing or unidentified, and any ages that were over 110 years old, a total of 93,889 cases were included in this analysis.
Dependent variable Healthcare utilization was the dependent variable, as measured by the frequency of contacts, namely how many times the patient had visited inpatient services, outpatient services and emergency room services, as well as total expenditure on healthcare services each year. The diagnoses and procedures for appendicitis were used for outcome assessment, which were classified using ICD-9. ICD-9 code 540.9 was classified as a normal case of appendicitis, and codes 540.0 and 540.13e7 were classified as cases of ruptured appendicitis.
Independent variable The main independent variable was nationality. All patients were classified as nationals or migrants using their identification numbers. For migrants, their personal identification numbers are encrypted in terms of their Alien Resident Certificate numbers and contain less than 10 digits. Nationals are encrypted using their personal identification numbers, which contain 10 digits. Using this difference, nationals and migrants were identified in the database based on the length of their identification numbers.
Controlled variables For healthcare utilization, the study controlled for gender, age, enrolment months in each year and socio-economic status. Ages were calculated by date of birth and categorized into six groups: 20e24, 25e34, 35e44, 45e54, 55e64 and 65 years. ‘Insurable wage’ serves as a proxy for socio-economic status. Socio-economic status was defined by the patients’ insurable wages in the databases. Under the NHI programme in Taiwan, two schemes are used to collect the premiums: by payroll deduction for those people with a well-defined monthly wage, such as government officers, employers, employees, and public or private teachers; and by a head tax for those without a well-defined monthly wage. People with well-defined monthly wages are classified into three categories: insurable wageNT$40,000 (US$1143). Those people without a welldefined monthly wage tend to be vulnerable subpopulations, such as farmers and low-income persons, and hence are grouped separately. They can enrol in the NHI programme through associations, such as farmers’ associations, or through local government offices. Thus, they were categorized
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as individuals who had enrolled through associations, or ‘others’, including veterans, corner-store owners or lowincome people who had enrolled through local government offices.22e24 All individuals who had ever been enrolled in the NHI programme between 1996 and 2001 were included. As expected, the enrolment length differed between individuals. Thus, in the final model, the study controlled for each individual’s number of enrolment months. For the outcome assessment, the study controlled for patient characteristics and hospital characteristics. Health status was defined as whether the patient had any of the major diseases identified by the Bureau of National Health Insurance (BNHI). The BNHI’s major disease list contains 31 ‘major diseases’, such as cancer, transplant treatment and its complications, or acquired immunodeficiency syndrome, which are defined based on the IllnesseInjury Severity Index. The admitting hospital characteristics included ownership (public, not-for-profit and for-profit), accreditation level (academic medical centre, regional hospital, district hospital and clinic) and patient volume [adults admitted for appendicitis in each hospital annually, categorized into two categories: high (150) and low (<150)].
Statistical analysis For healthcare utilization, the crude utilization was calculated and then the adjusted utilization was estimated using a twopart model. The two-part model is used for a high proportion of non-users. Since the distribution of healthcare utilization is highly skewed, logistic regression was used to estimate the probability of healthcare utilization in the first part of the model. The second part of the model used linear regression to predict the level of cost conditional on incurring any healthcare utilization. Furthermore, the c2 test was used to compare the unadjusted differences in ruptured appendicitis rates between nationals and migrants. Multiple logistic regression was used to obtain the odds ratios and their 95% confidence intervals. A significance level of a ¼ 0.05 was selected. All analyses were conducted using SAS for Windows, Version 9.1 (SAS Institute Inc, Cary, NC, USA) and STATA 8.0 (STATA Corp, College Station, TX, USA).
Results Figs. 1 and 2 show the trends in healthcare utilization and expenditure of nationals and migrants under the NHI programme in Taiwan from 1996 to 2001. Between 1996 and 2001, the overall healthcare utilization by migrants was much lower than that of nationals in terms of frequency of visits and total expenditure. After adjusting for gender, age, socio-economic status and enrolled months, the frequency of hospital visits and total expenditure on healthcare services per person remained lower among migrants than nationals. For example, on average, after adjusting for gender, age, socio-economic status and enrolled months, nationals used outpatient services 13.08 times per person per year in 1996 and 14.32 times per person per year in 2001; in comparison, migrants used outpatient services 0.93 and 2.86 times per person per year in 1996 and 2001, respectively. Similarly, the expenditure
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b
Inpatient 0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00
0.13
0.14
0.03 0.01 1996
1997
0.14
0.14
0.14
0.15
0.02
0.03
0.03
0.03
1999
2000
2001
1998
Outpatient
Frequency (person / year)
Frequency (person / year)
a
16.00 14.00 12.00 10.00 8.00 6.00 4.00 2.00 0.00
14.68
15.06
14.47
14.32
1.80
1.84
2.09
2.23
2.86
1997
1998
1999
2000
2001
13.98
13.08
0.93 1996
Year
Year Nationals
Nationals
Migrants
c
Emergency Room 0.25
Frequency (person / year)
Migrants
0.21
0.20
0.16
0.21
0.22
0.06
0.07
2000
2001
0.19
0.18
0.15 0.10
0.07
0.05
0.05 0.03
0.05 0.00
1996
1997
1998
1999 Year
Nationals
Migrants
Figure 1 e Trends in frequency of (a) inpatient, (b) outpatient and (c) emergency room visits from 1996 to 2001 among nationals and migrants.
for nationals was NT$8830 for outpatient services per person per year in 1996 and NT$11,893 per person per year in 2001. In contrast, the average expenditure for migrants was NT$541 and NT$1695 per person per year in 1996 and 2001,
b
Inpatient
7000 5000
4367
6384
5932
5797
5322
6000
4684
4000 3000 2000 1000
321
706
379
646
688
814
1998
1999
2000
2001
Outpatient
14000 Expenditure (NT / person)
Expenditure (NT /person)
a
respectively (Figs. 1 and 2). Over the 6 years of study, healthcare utilization increased among both nationals and migrants, but a significant gap still remained at the end of the study period.
12000 10000
10649
9687
8830
11433
11519
11893
1,196
1,295
1,695
1999
2000
2001
8000 6000 4000 2000
541
975
1,078
1996
1997
1998
0
0 1996
1997
Year
Year
Nationals
Nationals
Migrants
Expenditure (NT / person)
c
Migrants
Emergency Room
500
433
419
441
81
87
95
1999
2000
2001
382 400
337 297
300 200 89
85
76
1996
1997
1998
100 0
Year Nationals
Migrants
Figure 2 e Trends in expenditure on (a) inpatient, (b) outpatient and (c) emergency room visits from 1996 to 2001 among nationals and migrants.
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Table 2 e Details of adult patients with appendicitis admitted to hospital in Taiwan, 1996e2001. Total
No. of patients Nationality National Migrant Gender Female Male Age (years) 20e24 25e34 35e44 45e54 55e64 65 Major disease No Yes Insurable wage (NT$) <20,000 20,000e40,000 40,000 Farmers/fishermen Others Hospital ownership Public Not-for-profit For-profit Accreditation level Medical centre Regional hospital District hospital Clinic Patient volume (cases per year) Low (<150) High (150)
Appendiceal perforation n
Rate (%)
93,889
24,603
26.20
90,813 (96.72%) 3076 (3.28%)
23,932 671
26.35 21.81
43,795 (46.65%) 50,094 (53.35%)
9851 14,752
22.49 29.45
15,271 (16.26%) 27,432 (29.22%) 21,930 (23.36%) 12,020 (12.80%) 7625 (8.12%) 9611 (10.24%)
2719 5400 5436 3655 2891 4502
17.80 19.69 24.79 30.41 37.91 46.84
92,320 (98.33%) 1569 (1.67%)
24,020 583
26.02 37.16
32,537 (34.65%) 19,884 (21.18%) 12,738 (13.57%) 13,628 (14.52%) 15,102 (16.08%)
7954 4679 3250 4573 4147
24.45 23.53 25.51 33.56 27.46
19,702 (20.98%) 38,666 (41.18%) 35,521 (37.83%)
4689 10,321 9593
23.80 26.69 27.01
22,222 (23.67%) 36,877 (39.28%) 34,240 (36.47%) 550 (0.59%)
6091 9649 8717 146
27.41 26.17 25.46 26.55
13,689 (14.58%) 80,200 (85.42%)
3661 20,942
26.74 26.11
P*
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
0.1202
*c2 test.
Table 2 shows the rupture rates for appendicitis among nationals and migrants. In total, 93,889 patients aged 20 years had an appendectomy or drainage of an appendiceal abscess between 1996 and 2001. Of these, 90,813 (96.72%) were nationals and 3076 (3.28%) were migrants. Overall, the crude rate of appendiceal perforation was significantly higher for nationals than for migrants (26.35% and 21.81%, respectively; P < 0.001). Table 3 shows the adjusted risk factor results for appendicitis perforation among adults in Taiwan between 1996 and 2001. After controlling for patient characteristics (gender, age, major disease and insurable wage) and hospital characteristics (hospital ownership, accreditation level and patient volume), the odds of perforation was only 1.01 times higher for migrants than for nationals, and thus the risk of perforation was not significantly higher for migrants (P ¼ 0.770). Nevertheless, consistent with other research, the rate of ruptured appendicitis did increase with age,4 with insurable income status9 and was also higher for males.4 Furthermore, there appears to be a higher risk of perforation among patients admitted to not-for-profit and for-profit hospitals compared with public hospitals, academic medical centres and academic hospitals. This also seemed to be true for units and
hospitals with a lower patient volume compared with those with a higher patient volume.
Discussion This is the first population-based study to assess disparities between nationals and migrants in an Asian country. Consistent with previous research,15,21,25e32 this study found that migrants have a lower rate of healthcare utilization, and this gap persisted over the 6-year study period. Two hypotheses, ‘access barrier’ and the ‘healthy immigrant effect’, have been put forward to explain this in previous studies. In the first hypothesis, it is suggested that there are barriers to access to care for migrants due to lack of familiarity with the system. This then places them in a vulnerable situation. In Taiwan, the majority of the migrants come from Thailand, Indonesia and the Philippines, where the native language is not Chinese, and thus migrants may face both language and cultural barriers that hinder access to healthcare services and lead to lower healthcare utilization. Alternatively, the ‘healthy immigrant effect’ suggests that migrants tend to be healthier than
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Table 3 e Multiple logistic regression analysis of the risk factors for perforation in adults with appendicitis in Taiwan, 1996e2001. Odds ratio Nationality Nationals 1.00 Migrants 1.01 (0.93e1.11) Gender Female 1.00 Male 1.47 (1.42e1.51) Age (years) 20e24 1.00 25e34 1.11 (1.05e1.16) 35e44 1.49 (1.41e1.57) 45e54 1.99 (1.88e2.11) 55e64 2.79 (2.61e2.97) 65 3.99 (3.76e4.24) Major disease No 1.00 Yes 1.28 (1.15e1.42) Insurable wage (NT$) <20,000 1.00 20,000e40,000 0.94 (0.90e0.98) 40,000 0.89 (0.85e0.94) Farmers/fishermen 1.05 (1.00e1.10) Others 1.03 (0.99e1.08) Hospital ownership Public 1.00 Not-for-profit 1.23 (1.18e1.28) For-profit 1.36 (1.30e1.43) Accreditation level Medical centre 1.00 Regional hospital 0.94 (0.90e0.97) District hospital 0.84 (0.80e0.88) Clinic 0.80 (0.65e0.98) Patient volume (cases per year) Low (<150) 1.00 High (150) 0.91 (0.87e0.96)
P
0.762
<0.001
<0.001 <0.001 <0.001 <0.001 <0.001
<0.001
0.004 <0.001 0.058 0.152
<0.001 <0.001
0.001 <0.001 0.033
<0.001
Values in parentheses are 95% confidence intervals.
nationals. Firstly, due to self-selection, healthy people are more likely to migrate, perhaps because they have a better social network,32 and only some people want to or have the financial ability to emigrate.33 Secondly, because of the presence of health screening for migrants when moving to a new country, the newcomers might be generally healthier than nationals.18,19 According to Taiwan’s statistics,34 more than three-quarters of all migrants to Taiwan are labourers. Since they need a better health status to sustain their heavy workload, this ought to lead to a lower rate of healthcare utilization among such migrants. Moreover, despite the lower utilization of the NHI system by migrants, a more interesting question is whether they have a worse outcome when they face an acute surgical emergency, such as acute appendicitis. The results demonstrate that the outcome in terms of the rupture rate for appendicitis does not differ between these two groups under the NHI programme in Taiwan. This suggests that migrants’ access to care, at least for an emergency surgical condition, is not as bad as many people have speculated, and the ‘healthy immigrant effect’ would seem, in general, to be a better explanation of their lower healthcare utilization.
In terms of outcome, the rate of ruptured appendicitis was similar between nationals and migrants. Compared with previous literature, there are three possible differences in context. Firstly, the study setting in Greece was in rural areas and this contrasts with Taiwan where most migrants live in urban areas. With high numbers of healthcare facilities located in urban areas, the difference in physical or geographical access to the necessary care among nationals and migrants in Taiwan may not have been as large as that observed in the Greek study. Secondly, since the Greek study was based in a provincial hospital, the migrants who were sent to more advanced facilities may have had a worse medical status than the Greek nationals. This contrasts with the present study, which used population-based data and therefore suffers less from the issue of selection. Furthermore, the present study was somewhat closer to the findings in the USA, where migrants did not have a worse health outcome due to hindered access to care. Nevertheless, in the US studies, it was found that migrants had better outcomes in some disease categories, possibly due to confounding effects associated with their insurance status. There are a few limitations to this study that should be noted. Firstly, misdiagnosis of acute appendicitis may have overestimated the occurrence of appendicitis, and this would cause an underestimation of the perforation rate. It is possible that the misdiagnosis rate may differ between migrants and nationals, but there is no evidence to support this in Taiwan. However, it is possible that misdiagnosis is less likely to occur among people who have better access to and a better understanding of the healthcare services, such as nationals. In these circumstances, the use of a surgical diagnosis such as appendicitis may underestimate the difference in perforation risk between nationals and migrants. Secondly, owing to data limitations, it was not possible to extend the study beyond 2001 due to an administrative change in 2002, as it is no longer possible to separate migrants from nationals by the length of their encrypted identification numbers. Thirdly, each disease has its own characteristics. Therefore, using a non-discretionary health condition, such as ruptured appendicitis, to investigate the access to health care can be misleading and may not generalize to all conditions. For example, someone faced with an appendicitis crisis in the middle of the night may need to seek and access care immediately, irrespective of their access status, especially in the context of the absence of structural barriers to care. Therefore, future research may advance this study by extending the investigation to other diseases. Furthermore, in this Asian study, the vast majority of migrants came from South-East Asia with a variety of languages, cultures and lifestyles. Thus, the results cannot be applied to migrants who come from other countries, such as Europe or the USA. Fourthly, comparing a small group with a larger group may overestimate the statistical significance. Hence, the true level of statistical significance may be larger than observed (odds ratio 1.01, 95% confidence interval 0.93w1.11), and the difference would be even less significant. Fifthly, according to the Nationality Act, foreign spouses are able to apply for naturalization and thus their identification numbers become the same as nationals; therefore, there may be some misclassification of foreign spouses who have resided in Taiwan for more than 3 years, which would result in
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underestimation. Finally, as only the NHI databases were used in this study, the data cannot be generalized to those who are not enrolled in the NHI programme. In conclusion, under the NHI system in Taiwan, although migrants may not use healthcare services as frequently or as intensively as nationals, their outcome did not differ from that of Taiwanese nationals when facing a surgical emergency. Providing health insurance for migrants may help to ensure their access to emergency care, and thus will reduce any potential adverse outcomes. Consequently, the authors are of the opinion that the findings lean toward the ‘healthy immigrant effect’, whereby the lower healthcare utilization is not necessarily due to worse access to care but may be due to the fact that migrants are healthier than nationals. In addition, the authors suggest that the use of a single indicator to measure access disparity between nationals and migrants may yield misleading inferences. A combination of utilization and outcome indicator(s) allows one to better evaluate disparities in access to care.
Ethical approval None sought.
Funding The study was supported by a grant from Taiwan’s Ministry of Education, Aim for the Top University Plan, and Taiwan’s National Health Research Institute (94A1-HPSP01-01).
Competing interests None declared.
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9. Huang N, Yip W, Chang HJ, Chou YJ. Trends in rural and urban differentials in incidence rates for ruptured appendicitis under the National Health Insurance in Taiwan. Public Health 2006;120:1055e63. 10. Simich L, Beiser M, Stewart M, Mwakarimba E. Providing social support for immigrants and refugees in Canada: challenges and directions. J Immigr Health 2005;7:259e68. 11. Ponce NA, Hays RD, Cunningham WE. Linguistic disparities in health care access and health status among older adults. J Gen Intern Med 2006;21:786e91. 12. Wingo PA, Kulkarni A, Borrud LG, McDonald JA, Villalobos SA, Green DC. Health disparities among Mexican American women aged 15e44 years: National Health and Nutrition Examination Survey, 1999e2004. Am J Public Health 2009;99: 1300e7. 13. Newbold KB. Self-rated health within the Canadian immigrant population: risk and the healthy immigrant effect. Soc Sci Med 2005;60:1359e70. 14. Saint-Jean G, Crandall LA. Utilization of preventive care by Haitian immigrants in Miami, Florida. J Immigr Health 2005;7: 283e92. 15. Mohanty SA, Woolhandler S, Himmelstein DU, Pati S, Carrasquillo O, Bor DH. Health care expenditures of immigrants in the United States: a nationally representative analysis. Am J Public Health 2005;95:1431e8. 16. DesMeules M, Gold J, Kazanjian A, Manuel D, Payne J, Vissandee B, et al. New approaches to immigrant health assessment. Can J Public Health 2004;95:I22e6. 17. Lucas JW, Barr-Anderson DJ, Kington RS. Health status, health insurance, and health care utilization patterns of immigrant Black men. Am J Public Health 2003;93:1740e7. 18. Antecol H, Bedard K. Unhealthy assimilation: why do immigrants converge to American health status levels? Demography 2006;43:337e60. 19. McDonald JT, Kennedy S. Insights into the ‘healthy immigrant effect’: health status and health service use of immigrants to Canada. Soc Sci Med 2004;59:1613e27. 20. Muennig P, Jia H, Khan K. Hospitalization for heart disease, stroke, and diabetes mellitus among Indian-born persons: a small area analysis. BMC Cardiovasc Disord 2004;4:19. 21. Muennig P, Jia H, Khan K, Pallin DJ. Ascertaining variation in hospitalization risk among immigrants using small area analysis. Prev Med 2006;43:145e9. 22. Chen LS, Chou YJ, Tsay JH, Lee CH, Chou P, Huang N. Variation in the cervical cancer screening compliance among women with disability. J Med Screen 2009;16:85e90. 23. Chien IC, Hsu JH, Lin CH, Bih SH, Chou YJ, Chou P. Prevalence of diabetes in patients with schizophrenia in Taiwan: a population-based National Health Insurance study. Schizophr Res 2009;111:17e22. 24. Chou YA, Chou YJ, Lee CH, Huang N. Pregnancy outcomes among native and foreign-born women in Taiwan: maternal health utilization. J Womens Health (Larchmt) 2008;17:1505e12. 25. Arcury TA, Gesler WM, Preisser JS, Sherman J, Spencer J, Perin J. The effects of geography and spatial behavior on health care utilization among the residents of a rural region. Health Serv Res 2005;40:135e55. 26. Axen E, Lindstrom M. Ethnic differences in self-reported lack of access to a regular doctor: a population-based study. Ethn Health 2002;7:195e207. 27. Lofters A, Glazier RH, Agha MM, Creatore MI, Moineddin R. Inadequacy of cervical cancer screening among urban recent immigrants: a population-based study of physician and laboratory claims in Toronto, Canada. Prev Med 2007;44:536e42. 28. Morenoff JD, House JS, Hansen BB, Williams DR, Kaplan GA, Hunte HE. Understanding social disparities in hypertension prevalence, awareness, treatment, and
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control: the role of neighborhood context. Soc Sci Med 2007; 65:1853e66. 29. Read JG, Amick B, Donato KM. Arab immigrants: a new case for ethnicity and health? Soc Sci Med 2005;61:77e82. 30. Rhodes P, Nocon A, Wright J. Access to diabetes services: the experiences of Bangladeshi people in Bradford, UK. Ethn Health 2003;8:171e88. 31. Taylor RJ, Morrell SL, Mamoon HA, Macansh S, Ross J, Wain GV. Cervical cancer screening in a Vietnamese nominal cohort. Ethn Health 2003;8:251e61.
32. Viruell-Fuentes EA. Beyond acculturation: immigration, discrimination, and health research among Mexicans in the United States. Soc Sci Med 2007;65:1524e35. 33. Feliciano C. Educational selectivity in U.S. immigration: how do immigrants compare to those left behind? Demography 2005;42:131e52. 34. Department of Statistics, Ministry of the Interior. Statistical Yearbook of Interior 2002. Department of Statistics, Ministry of the Interior, Taiwan, R.O.C., 2002. Available from: www. moi.gov.tw/stat [accessed 08.04.09].
available at www.sciencedirect.com
Public Health journal homepage: www.elsevierhealth.com/journals/pubh
Original Research
Comparison of the perforation rate for acute appendicitis between nationals and migrants in Taiwan, 1996e2001 T-L. Liu a, J-H. Tsay b, Y-J. Chou a, N. Huang c,* a
Institute of Public Health, National Yang-Ming University, Taipei, Taiwan, ROC Department of Social Work, College of Social Science, National Taiwan University, Taipei, Taiwan, ROC c Institute of Hospital and Health Care Administration, National Yang-Ming University, No. 155, Sec. 2, Li-Nong St., Taipei 11221, Taiwan, ROC b
article info
summary
Article history:
Objective: Immigrant populations have grown rapidly in recent years in many countries.
Received 3 October 2009
Immigrant-related healthcare issues have thus become more and more important. The aim
Received in revised form
of this study was to assess any possible disparity in access to care between migrants and
27 April 2010
nationals under the national health insurance (NHI) system in Taiwan.
Accepted 21 May 2010
Study design: Retrospective population-based observational study.
Available online 16 August 2010
Methods: National population-based data on patients aged 20 years in Taiwan under the NHI programme were studied. The frequency of use and expenditure on ambulatory care, inpatient
Keywords:
care and emergency care were analysed separately. Ruptured appendicitis was also analysed as
Access to care
an outcome indicator for access to care. Logistic regression and two-part models were applied.
Healthcare utilization
Results: Overall, migrants had a lower rate of healthcare utilization than nationals, and this
Appendicitis
gap remained consistent from 1996 to 2001. However, using ruptured appendicitis as the
Migrants
outcome indicator, no significant overall difference in access to care was found between
Taiwan
nationals and migrants under the NHI programme in Taiwan (odds ratio 1.01, 95% confidence interval 0.93w1.11). Conclusion: This study found that although migrants had a lower rate of healthcare utilization than nationals, their rate of adverse outcome was similar to nationals when they faced an acute, non-selective emergency condition such as appendicitis. The findings suggest that the use of more dimensional indicators may help to avoid possible misleading inferences on the variation in access to health care in Taiwan. ª 2010 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved.
Introduction Disparity in access to care is a critical public health concern.1 ‘Equity of accessibility comprises how systematic differences are in using health care services and what are the outcomes
among various groups and the barriers that cause these differences.’2 Therefore, in addition to general healthcare utilization, a number of researchers have used appendicitis as a distinct indicator of access to care when assessing disparities among disadvantaged subpopulations.3e9 Acute
* Corresponding author. Tel.: þ886 2 2826 7372; fax: þ886 2 2826 1002. E-mail address: [email protected] (N. Huang). 0033-3506/$ e see front matter ª 2010 The Royal Society for Public Health. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.puhe.2010.05.009
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appendicitis is commonly used as the model outcome because it is one of the most common clinical problems in surgery. Most research has focused on differences between races, such as between Black and White populations in the USA, or on different types of insurance within a population. Only a limited number of studies have targeted migrants. With globalization, migrant populations have grown rapidly in recent years and their health-related issues have become increasingly important. Healthcare access is one major factor. Many have speculated that there may be access barriers associated with such a life transition; these include immigration and settlement,10 language disadvantage,11 lack of acculturation,12 unfamiliarity or distrust of the healthcare system,13 and a lack of legal status.14 These barriers may cause migrants to have difficulty with timely access to appropriate health services when adapting to a new environment, which could put them in a vulnerable situation. Several studies have used healthcare utilization as an indicator that allows assessment of possible disparities in access to care. These studies found that migrants had lower healthcare utilization than nationals.15e17 However, the lower healthcare utilization observed among migrants does not necessarily mean that there are disparities in access barriers. It could mean that migrants are healthier than nationals, which is known as the ‘healthy immigrant effect’.18,19 Hence, when assessing possible disparities in access to care between migrants and nationals, one should also pay attention to their health outcomes. Although there is evidence showing that migrants have lower healthcare utilization in general than nationals, there is very limited empirical evidence on their emergency surgical outcomes. Three studies have investigated health outcomes; two of these studies compared foreign-born and native-born populations in the USA using the preventable hospitalization rate for different diagnostic diseases,20,21 and the other study compared migrants and non-migrants in Greece using ruptured appendicitis as the indicator.8 The two US studies found that migrants tend to have a lower preventable hospitalization rate than nationals, and the study in Greece found that migrants have a significantly worse rate for ruptured appendicitis than non-migrants. Hence, the present study tried to assess any disparities in healthcare utilization between nationals and migrants under the national health insurance (NHI) programme in Taiwan between 1996 and 2001. In this study, ruptured appendicitis was used as an outcome indicator for access to care. Taiwan is an interesting setting in which to study this important research question. Firstly, similar to many Asian countries, the number of migrants in Taiwan is increasing rapidly; migrants represented approximately 1.7% of the total population in 2001. Therefore, access to care among migrants is becoming a major concern. Secondly, the NHI programme in Taiwan provides comprehensive coverage to all citizens and also to legal migrants with employment or who have lived in Taiwan for more than 4 months, as well as the dependents of such persons. Hence, studying the enrollees of the NHI programme avoids the confounding effect of insurance status. Thirdly, the population-based NHI datasets enable the minimization of selection bias which occurs when using hospitalbased datasets. The aim was to determine if accessibility to
the healthcare system is significantly worse among migrants than among nationals. Overall, this study may help to improve understanding of whether disparities in access to care exist between migrants and nationals under a universal and comprehensive health insurance programme in an Asian society.
Methods Data sources and study population In order to meet the study objectives, HDATA was used to compare healthcare utilization between migrants and nationals. HDATA is an NHI meta-database, constructed and managed by the National Health Research Institute. It links the NHI sample files and the death certificates for a random sample of 200,000 NHI beneficiaries out of a population of 21,400,826 enrolees who had ever been enrolled between 1995 and 2000. It contains comprehensive enrolment and utilization information for this random sample, which includes identification number, gender, date of birth, months of enrolment, expenditure amounts and insurable wage. The NHI sample files have also been linked to death certificates in HDATA. Those people who died during each particular year and those with incomplete data were excluded to calculate healthcare utilization. The distribution of the sample by year is presented in Table 1. Due to the small number of cases of appendicitis in the HDATA sample, an alternative data source was used to investigate the second objective. Instead of using the sample files, the 1996e2001 NHI inpatient claims files, enrolment files, major diseases files and hospital registry were used to identify all cases of appendicitis. The NHI inpatient file provided information on gender, date of birth, dates of admission and discharge, medical diagnosis and treatment codes, expenditure amounts and hospital identifier. The NHI enrolment files provided the patients’ insurable wage, and the major diseases files helped to identify patients with a major disease, as well as the type of major disease. Furthermore, the NHI hospital files provided information on the certification level, ownership and patient volume of the admitting hospitals. The linkage of the datasets was carried out using encrypted personal identification numbers, hospital identifiers and dates of birth; these procedures followed the guidelines of the
Table 1 e Descriptive statistics of the population in assessing healthcare utilization under the national health insurance programme in Taiwan, 1996e2001. Total
1996 1997 1998 1999 2000 2001
119,742 122,618 126,048 129,073 131,362 133,603
Nationals
Migrants
n
%
n
%
117,812 120,206 122,853 125,324 127,111 130,770
98.39 98.03 97.47 97.10 96.76 97.88
1930 2412 3195 3749 4251 2833
1.61 1.97 2.53 2.90 3.24 2.12
p u b l i c h e a l t h 1 2 4 ( 2 0 1 0 ) 5 6 5 e5 7 2
National Health Research Institute. From the populationbased inpatient file, it was possible to identify 95,193 patients with appendicitis by International Classification of Disease 9th Revision (ICD-9) code (540.0, 540.1 and 540.9) who were aged 20 years during the study period (1996e2001). To avoid misclassification, only those cases where the principal procedure was appendectomy or the drainage of an appendiceal abscess (ICD operation codes 47.0 and 47.2) were captured. After excluding patients whose gender was missing or unidentified, and any ages that were over 110 years old, a total of 93,889 cases were included in this analysis.
Dependent variable Healthcare utilization was the dependent variable, as measured by the frequency of contacts, namely how many times the patient had visited inpatient services, outpatient services and emergency room services, as well as total expenditure on healthcare services each year. The diagnoses and procedures for appendicitis were used for outcome assessment, which were classified using ICD-9. ICD-9 code 540.9 was classified as a normal case of appendicitis, and codes 540.0 and 540.13e7 were classified as cases of ruptured appendicitis.
Independent variable The main independent variable was nationality. All patients were classified as nationals or migrants using their identification numbers. For migrants, their personal identification numbers are encrypted in terms of their Alien Resident Certificate numbers and contain less than 10 digits. Nationals are encrypted using their personal identification numbers, which contain 10 digits. Using this difference, nationals and migrants were identified in the database based on the length of their identification numbers.
Controlled variables For healthcare utilization, the study controlled for gender, age, enrolment months in each year and socio-economic status. Ages were calculated by date of birth and categorized into six groups: 20e24, 25e34, 35e44, 45e54, 55e64 and 65 years. ‘Insurable wage’ serves as a proxy for socio-economic status. Socio-economic status was defined by the patients’ insurable wages in the databases. Under the NHI programme in Taiwan, two schemes are used to collect the premiums: by payroll deduction for those people with a well-defined monthly wage, such as government officers, employers, employees, and public or private teachers; and by a head tax for those without a well-defined monthly wage. People with well-defined monthly wages are classified into three categories: insurable wage
567
as individuals who had enrolled through associations, or ‘others’, including veterans, corner-store owners or lowincome people who had enrolled through local government offices.22e24 All individuals who had ever been enrolled in the NHI programme between 1996 and 2001 were included. As expected, the enrolment length differed between individuals. Thus, in the final model, the study controlled for each individual’s number of enrolment months. For the outcome assessment, the study controlled for patient characteristics and hospital characteristics. Health status was defined as whether the patient had any of the major diseases identified by the Bureau of National Health Insurance (BNHI). The BNHI’s major disease list contains 31 ‘major diseases’, such as cancer, transplant treatment and its complications, or acquired immunodeficiency syndrome, which are defined based on the IllnesseInjury Severity Index. The admitting hospital characteristics included ownership (public, not-for-profit and for-profit), accreditation level (academic medical centre, regional hospital, district hospital and clinic) and patient volume [adults admitted for appendicitis in each hospital annually, categorized into two categories: high (150) and low (<150)].
Statistical analysis For healthcare utilization, the crude utilization was calculated and then the adjusted utilization was estimated using a twopart model. The two-part model is used for a high proportion of non-users. Since the distribution of healthcare utilization is highly skewed, logistic regression was used to estimate the probability of healthcare utilization in the first part of the model. The second part of the model used linear regression to predict the level of cost conditional on incurring any healthcare utilization. Furthermore, the c2 test was used to compare the unadjusted differences in ruptured appendicitis rates between nationals and migrants. Multiple logistic regression was used to obtain the odds ratios and their 95% confidence intervals. A significance level of a ¼ 0.05 was selected. All analyses were conducted using SAS for Windows, Version 9.1 (SAS Institute Inc, Cary, NC, USA) and STATA 8.0 (STATA Corp, College Station, TX, USA).
Results Figs. 1 and 2 show the trends in healthcare utilization and expenditure of nationals and migrants under the NHI programme in Taiwan from 1996 to 2001. Between 1996 and 2001, the overall healthcare utilization by migrants was much lower than that of nationals in terms of frequency of visits and total expenditure. After adjusting for gender, age, socio-economic status and enrolled months, the frequency of hospital visits and total expenditure on healthcare services per person remained lower among migrants than nationals. For example, on average, after adjusting for gender, age, socio-economic status and enrolled months, nationals used outpatient services 13.08 times per person per year in 1996 and 14.32 times per person per year in 2001; in comparison, migrants used outpatient services 0.93 and 2.86 times per person per year in 1996 and 2001, respectively. Similarly, the expenditure
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p u b l i c h e a l t h 1 2 4 ( 2 0 1 0 ) 5 6 5 e5 7 2
b
Inpatient 0.20 0.18 0.16 0.14 0.12 0.10 0.08 0.06 0.04 0.02 0.00
0.13
0.14
0.03 0.01 1996
1997
0.14
0.14
0.14
0.15
0.02
0.03
0.03
0.03
1999
2000
2001
1998
Outpatient
Frequency (person / year)
Frequency (person / year)
a
16.00 14.00 12.00 10.00 8.00 6.00 4.00 2.00 0.00
14.68
15.06
14.47
14.32
1.80
1.84
2.09
2.23
2.86
1997
1998
1999
2000
2001
13.98
13.08
0.93 1996
Year
Year Nationals
Nationals
Migrants
c
Emergency Room 0.25
Frequency (person / year)
Migrants
0.21
0.20
0.16
0.21
0.22
0.06
0.07
2000
2001
0.19
0.18
0.15 0.10
0.07
0.05
0.05 0.03
0.05 0.00
1996
1997
1998
1999 Year
Nationals
Migrants
Figure 1 e Trends in frequency of (a) inpatient, (b) outpatient and (c) emergency room visits from 1996 to 2001 among nationals and migrants.
for nationals was NT$8830 for outpatient services per person per year in 1996 and NT$11,893 per person per year in 2001. In contrast, the average expenditure for migrants was NT$541 and NT$1695 per person per year in 1996 and 2001,
b
Inpatient
7000 5000
4367
6384
5932
5797
5322
6000
4684
4000 3000 2000 1000
321
706
379
646
688
814
1998
1999
2000
2001
Outpatient
14000 Expenditure (NT / person)
Expenditure (NT /person)
a
respectively (Figs. 1 and 2). Over the 6 years of study, healthcare utilization increased among both nationals and migrants, but a significant gap still remained at the end of the study period.
12000 10000
10649
9687
8830
11433
11519
11893
1,196
1,295
1,695
1999
2000
2001
8000 6000 4000 2000
541
975
1,078
1996
1997
1998
0
0 1996
1997
Year
Year
Nationals
Nationals
Migrants
Expenditure (NT / person)
c
Migrants
Emergency Room
500
433
419
441
81
87
95
1999
2000
2001
382 400
337 297
300 200 89
85
76
1996
1997
1998
100 0
Year Nationals
Migrants
Figure 2 e Trends in expenditure on (a) inpatient, (b) outpatient and (c) emergency room visits from 1996 to 2001 among nationals and migrants.
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Table 2 e Details of adult patients with appendicitis admitted to hospital in Taiwan, 1996e2001. Total
No. of patients Nationality National Migrant Gender Female Male Age (years) 20e24 25e34 35e44 45e54 55e64 65 Major disease No Yes Insurable wage (NT$) <20,000 20,000e40,000 40,000 Farmers/fishermen Others Hospital ownership Public Not-for-profit For-profit Accreditation level Medical centre Regional hospital District hospital Clinic Patient volume (cases per year) Low (<150) High (150)
Appendiceal perforation n
Rate (%)
93,889
24,603
26.20
90,813 (96.72%) 3076 (3.28%)
23,932 671
26.35 21.81
43,795 (46.65%) 50,094 (53.35%)
9851 14,752
22.49 29.45
15,271 (16.26%) 27,432 (29.22%) 21,930 (23.36%) 12,020 (12.80%) 7625 (8.12%) 9611 (10.24%)
2719 5400 5436 3655 2891 4502
17.80 19.69 24.79 30.41 37.91 46.84
92,320 (98.33%) 1569 (1.67%)
24,020 583
26.02 37.16
32,537 (34.65%) 19,884 (21.18%) 12,738 (13.57%) 13,628 (14.52%) 15,102 (16.08%)
7954 4679 3250 4573 4147
24.45 23.53 25.51 33.56 27.46
19,702 (20.98%) 38,666 (41.18%) 35,521 (37.83%)
4689 10,321 9593
23.80 26.69 27.01
22,222 (23.67%) 36,877 (39.28%) 34,240 (36.47%) 550 (0.59%)
6091 9649 8717 146
27.41 26.17 25.46 26.55
13,689 (14.58%) 80,200 (85.42%)
3661 20,942
26.74 26.11
P*
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
<0.001
0.1202
*c2 test.
Table 2 shows the rupture rates for appendicitis among nationals and migrants. In total, 93,889 patients aged 20 years had an appendectomy or drainage of an appendiceal abscess between 1996 and 2001. Of these, 90,813 (96.72%) were nationals and 3076 (3.28%) were migrants. Overall, the crude rate of appendiceal perforation was significantly higher for nationals than for migrants (26.35% and 21.81%, respectively; P < 0.001). Table 3 shows the adjusted risk factor results for appendicitis perforation among adults in Taiwan between 1996 and 2001. After controlling for patient characteristics (gender, age, major disease and insurable wage) and hospital characteristics (hospital ownership, accreditation level and patient volume), the odds of perforation was only 1.01 times higher for migrants than for nationals, and thus the risk of perforation was not significantly higher for migrants (P ¼ 0.770). Nevertheless, consistent with other research, the rate of ruptured appendicitis did increase with age,4 with insurable income status9 and was also higher for males.4 Furthermore, there appears to be a higher risk of perforation among patients admitted to not-for-profit and for-profit hospitals compared with public hospitals, academic medical centres and academic hospitals. This also seemed to be true for units and
hospitals with a lower patient volume compared with those with a higher patient volume.
Discussion This is the first population-based study to assess disparities between nationals and migrants in an Asian country. Consistent with previous research,15,21,25e32 this study found that migrants have a lower rate of healthcare utilization, and this gap persisted over the 6-year study period. Two hypotheses, ‘access barrier’ and the ‘healthy immigrant effect’, have been put forward to explain this in previous studies. In the first hypothesis, it is suggested that there are barriers to access to care for migrants due to lack of familiarity with the system. This then places them in a vulnerable situation. In Taiwan, the majority of the migrants come from Thailand, Indonesia and the Philippines, where the native language is not Chinese, and thus migrants may face both language and cultural barriers that hinder access to healthcare services and lead to lower healthcare utilization. Alternatively, the ‘healthy immigrant effect’ suggests that migrants tend to be healthier than
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Table 3 e Multiple logistic regression analysis of the risk factors for perforation in adults with appendicitis in Taiwan, 1996e2001. Odds ratio Nationality Nationals 1.00 Migrants 1.01 (0.93e1.11) Gender Female 1.00 Male 1.47 (1.42e1.51) Age (years) 20e24 1.00 25e34 1.11 (1.05e1.16) 35e44 1.49 (1.41e1.57) 45e54 1.99 (1.88e2.11) 55e64 2.79 (2.61e2.97) 65 3.99 (3.76e4.24) Major disease No 1.00 Yes 1.28 (1.15e1.42) Insurable wage (NT$) <20,000 1.00 20,000e40,000 0.94 (0.90e0.98) 40,000 0.89 (0.85e0.94) Farmers/fishermen 1.05 (1.00e1.10) Others 1.03 (0.99e1.08) Hospital ownership Public 1.00 Not-for-profit 1.23 (1.18e1.28) For-profit 1.36 (1.30e1.43) Accreditation level Medical centre 1.00 Regional hospital 0.94 (0.90e0.97) District hospital 0.84 (0.80e0.88) Clinic 0.80 (0.65e0.98) Patient volume (cases per year) Low (<150) 1.00 High (150) 0.91 (0.87e0.96)
P
0.762
<0.001
<0.001 <0.001 <0.001 <0.001 <0.001
<0.001
0.004 <0.001 0.058 0.152
<0.001 <0.001
0.001 <0.001 0.033
<0.001
Values in parentheses are 95% confidence intervals.
nationals. Firstly, due to self-selection, healthy people are more likely to migrate, perhaps because they have a better social network,32 and only some people want to or have the financial ability to emigrate.33 Secondly, because of the presence of health screening for migrants when moving to a new country, the newcomers might be generally healthier than nationals.18,19 According to Taiwan’s statistics,34 more than three-quarters of all migrants to Taiwan are labourers. Since they need a better health status to sustain their heavy workload, this ought to lead to a lower rate of healthcare utilization among such migrants. Moreover, despite the lower utilization of the NHI system by migrants, a more interesting question is whether they have a worse outcome when they face an acute surgical emergency, such as acute appendicitis. The results demonstrate that the outcome in terms of the rupture rate for appendicitis does not differ between these two groups under the NHI programme in Taiwan. This suggests that migrants’ access to care, at least for an emergency surgical condition, is not as bad as many people have speculated, and the ‘healthy immigrant effect’ would seem, in general, to be a better explanation of their lower healthcare utilization.
In terms of outcome, the rate of ruptured appendicitis was similar between nationals and migrants. Compared with previous literature, there are three possible differences in context. Firstly, the study setting in Greece was in rural areas and this contrasts with Taiwan where most migrants live in urban areas. With high numbers of healthcare facilities located in urban areas, the difference in physical or geographical access to the necessary care among nationals and migrants in Taiwan may not have been as large as that observed in the Greek study. Secondly, since the Greek study was based in a provincial hospital, the migrants who were sent to more advanced facilities may have had a worse medical status than the Greek nationals. This contrasts with the present study, which used population-based data and therefore suffers less from the issue of selection. Furthermore, the present study was somewhat closer to the findings in the USA, where migrants did not have a worse health outcome due to hindered access to care. Nevertheless, in the US studies, it was found that migrants had better outcomes in some disease categories, possibly due to confounding effects associated with their insurance status. There are a few limitations to this study that should be noted. Firstly, misdiagnosis of acute appendicitis may have overestimated the occurrence of appendicitis, and this would cause an underestimation of the perforation rate. It is possible that the misdiagnosis rate may differ between migrants and nationals, but there is no evidence to support this in Taiwan. However, it is possible that misdiagnosis is less likely to occur among people who have better access to and a better understanding of the healthcare services, such as nationals. In these circumstances, the use of a surgical diagnosis such as appendicitis may underestimate the difference in perforation risk between nationals and migrants. Secondly, owing to data limitations, it was not possible to extend the study beyond 2001 due to an administrative change in 2002, as it is no longer possible to separate migrants from nationals by the length of their encrypted identification numbers. Thirdly, each disease has its own characteristics. Therefore, using a non-discretionary health condition, such as ruptured appendicitis, to investigate the access to health care can be misleading and may not generalize to all conditions. For example, someone faced with an appendicitis crisis in the middle of the night may need to seek and access care immediately, irrespective of their access status, especially in the context of the absence of structural barriers to care. Therefore, future research may advance this study by extending the investigation to other diseases. Furthermore, in this Asian study, the vast majority of migrants came from South-East Asia with a variety of languages, cultures and lifestyles. Thus, the results cannot be applied to migrants who come from other countries, such as Europe or the USA. Fourthly, comparing a small group with a larger group may overestimate the statistical significance. Hence, the true level of statistical significance may be larger than observed (odds ratio 1.01, 95% confidence interval 0.93w1.11), and the difference would be even less significant. Fifthly, according to the Nationality Act, foreign spouses are able to apply for naturalization and thus their identification numbers become the same as nationals; therefore, there may be some misclassification of foreign spouses who have resided in Taiwan for more than 3 years, which would result in
p u b l i c h e a l t h 1 2 4 ( 2 0 1 0 ) 5 6 5 e5 7 2
underestimation. Finally, as only the NHI databases were used in this study, the data cannot be generalized to those who are not enrolled in the NHI programme. In conclusion, under the NHI system in Taiwan, although migrants may not use healthcare services as frequently or as intensively as nationals, their outcome did not differ from that of Taiwanese nationals when facing a surgical emergency. Providing health insurance for migrants may help to ensure their access to emergency care, and thus will reduce any potential adverse outcomes. Consequently, the authors are of the opinion that the findings lean toward the ‘healthy immigrant effect’, whereby the lower healthcare utilization is not necessarily due to worse access to care but may be due to the fact that migrants are healthier than nationals. In addition, the authors suggest that the use of a single indicator to measure access disparity between nationals and migrants may yield misleading inferences. A combination of utilization and outcome indicator(s) allows one to better evaluate disparities in access to care.
Ethical approval None sought.
Funding The study was supported by a grant from Taiwan’s Ministry of Education, Aim for the Top University Plan, and Taiwan’s National Health Research Institute (94A1-HPSP01-01).
Competing interests None declared.
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