目的：計算2000年至2013年台灣肝臟移植發生率，並探討發生率之社會經濟地位差異。

方法：由健保資料庫中節擷取1997年至2013年期間，因為嚴重肝臟疾病住院或接受侵入性肝臟治療手術之成人患者為研究母群體。社經變項以投保地區之地理位置、都市化程度、家庭收入中位數，以及個人投保薪資為依據。接受肝臟移植者則是以受贈手術碼或診斷碼（手術碼75020B、50.5X，ICD-9診斷碼V42.7、V42.9）且手術日期介於2000至2013年的患者為描述性研究族群。本研究計算研究期間之肝臟移植發生率，並使用卜瓦松迴歸分析社經變項與肝臟移植發生率之相關性。

接著我們沿用前述研究母群體，先以人口學變項與共病計算肝臟移植傾向分數，選定傾向分數位於90百分位以上的族群作為世代研究族群，並使用Cox比例風險模式針對社經變項對肝臟移植發生的影響，並以Fine And Gray’s Competing Risk Model考慮樣本於追蹤期間之競爭死因進一步探討社經變項對於肝臟移植機會的影響。

結果：台灣成人肝臟移植的案例從2000-2001年的每兩年56例成長到2012-2013年每兩年880例。年齡標準化肝臟移植發生率男性由每兩年每百萬人口1.45人上升至16.63人，女性亦由0.79人上升至5.47人。55歲至64歲接受肝臟移植的發生率最高。投保地在高度都市化市鎮的居民有最高的肝臟移植發生率（男性每百萬人口20.18人，女性5.29人）。在控制潛在干擾因子後，卜瓦松迴歸模型顯示：高度都市化市鎮的肝臟移植發生率比顯著較高，為參考組的1.32倍（Adjusted Rate Ratio（IRR）1.32，95%（Confidence Interval） CI 1.21-1.44，p<0.0001）。

世代研究樣本最終截取研究族群共197,082人，追蹤期間發生肝臟移植的人數有2,204人。在考慮競爭死因，並同時控制傾向分數、共病、年齡及性別的模型下，分析發現：投保所在地之都市化程度較高的地區（Adjusted hazard ratio（HR）1.418，95% CI 1.279-1.571）、地理區域為中部（Adjusted HR 2.095，95% CI 1.585-2.768）、家庭收入中位數較高（Adjusted HR 1.248，95% CI 1.055-1.478），以及個人投保薪資在中位數以上者（Adjusted HR 1.679， 95% CI 1.482-1.903）有顯著較高的肝臟移植發生機會。

結論：即便過去十餘年台灣地區接受肝臟移植的發生率逐年提高，惟肝臟移植發生機會仍存在有顯著的地理區域，以及社會經濟狀況的不平等現象，這是否是現行對於肝臟移植法規，造成了低社會經濟地位之末期肝臟疾病患者接受肝臟移植之機會受限，值得未來進一步研究之探討。

SUMMARY
The impact of socioeconomic status (SES) on the access to liver transplantation (LT) has been widely published in Western countries. From Western to Eastern, there are differences between LTs including the indications and the choices between living donor liver transplantation (LDLT) or deceased donor liver transplantation (DDLT). The first part of this study is a descriptive epidemiology study, aiming to describe a fourteen-year trend of the prevalence of LT in Taiwan as well as assessing the sociodemographic impact on LT. The second part of this study is a cohort study to evaluate the socioeconomic disparities on access to LT. The data were extracted from National Health Insurance Research Database (NHIRD). We involved our study group using ICD-9-CM code and ICD-OP-CODE associated with severe liver diseases between 1997 and 2013. The calendar year, sex, and age were standardized. The effect of demographics and urbanization were assessed with Poisson Regression Analysis. We observed an increasing trend of LT prevalence from 2000 to 2013. Higher prevalence rate was noted in the age group between 55 and 64, male, and urban neighborhoods . As for the cohort study, we calculated a propensity score (PS) using binary logistic regression analysis for each case according to their sex, age, and comorbidities. We involved those whose PS is higher than ninetieth percentage to be our study group. Cox proportional hazard regression model and Fine and Gray’s competing risk model identified that patients who lived in urban region, Central and Northern Taiwan, highest income quartile neighborhoods, and had higher income had higher chance to LT. In conclusion, this study showed an increased trend of LT in Taiwan, and identified that SES and demographics would be a barrier to LT. Further studies are warranted to confirm the causal relationship.
Key Words: Liver transplantation, Socioeconomics, Urbanization

INTRODUCTION

The impact of SES on the access to LT has been widely published in Western Countries. However, there are differences between Western LT and Taiwanese LT. First, the indications for LT in Western countries involve more nonalcoholic steotohepatitis (NASH) while there are more liver transplanted for alcoholic or viral hepatitis associated cirrhosis and hepatocellular carcinoma in Taiwan. Second, DDLT comprised 80% of LT in America while LDLT comprised 80% of LT in Taiwan. When it comes to LDLT, we could not ignore the factors of donors, who are required to be within fifth degree relatives according to the Organ Transplant Act in Taiwan. The barrier to LT seems to be larger since the LDLT involves more socioeconomic burden for a family. The prevalence of hepatitis or alcoholism were reported to be clustered, which may contribute to the barrier. Therefore we conducted this study to evaluate the socioeconomic disparities on access to LT in Taiwan.

MATERIALS AND METHODS

The data were extracted from NHIRD between the year of 1997 and 2013. We chose our study cohort according to the ICD_9_CM code and ICD_OP_CODE which represented severe liver diseases. We identified region, urbanization, the income level of neighborhoods, and personal income to be the SES factors.
In the first part of study, we included the patients who were older than 18 years old and undergone LT between 2000 and 2013. The ICD_OP_CODE involved is 75020B or 50.5X, and the ICD_9_CM code involved is V42.7 or V42.9. The age and sex were standardized. We calculated the prevalence rate of LT, and used Poisson regression analysis to evaluate the relationship between sociodemographic factors and prevalence of LT.
In the second part, we involved the patients’ sex, age, and comorbidities into PS using binary logistic regression analysis. Then cases whose PS were greater than ninetieth percentile were taken into our analysis. PS, PS together with comorbidities, PS, comorbidities together with sex and age are respectively adjusted into Cox proportional hazard regression model and Fine and Gray’s competing risk model to evaluate the impact of SES on access to LT.

RESULTS AND DISCUSSION

Based on the medical order (liver organ receipt: 75022Bm 75021B, 75020B) and operation (liver transplantation: ICD-9-CM, 50.5X, V59.6, V42.7, V42.9) codes, we identified 3,020 patients who were older than 18 years old hospitalized for liver transplantation between 2000 and 2013. The biannual age-sex-standardized prevalence rate increased from 1.45 to 16.63 per million person for male, and from 0.79 to 5.47 for female. Patients at the age between 55 to 64 years old had the highest prevalence rate for LT. People who lived in the urban neighborhoods had highest prevalence rate for LT (Figure). Compared with that of the year of 2000-2001, the prevalence rate increased in the following years (Adjusted incidence rate ratio, AIRR from 2.35 to 9.68). When we put the age between 18 and 44 as reference group, the age between 45 and 54 and age between 55 and 64 had significantly higher prevalence rate. Male had higher LT prevalence compared with female (AIRR 2.74, 95% Confident Interval (CI) = 2.53-2.97). There were higher prevalence rate in urban neighborhood compared with satellite and rural neighborhood.
A total of 1,965,831 patients were hospitalized for liver-related condition. 197,082 patients had PS greater than the ninetieth percentile. 2,204 were LT recipients while 194,878 were not. The percentage of LT was highest in urban neighborhoods, Central Taiwan, and highest income quartile neighborhoods. People who had higher median income also had higher percentage of LT. Fine and Gray’s competing risk model identified that urban neighborhoods had higher hazard ratio (HR) for prevalence of LT (HR = 1.367, 95% CI = 1.233 – 1.514). Central Taiwan and Northern Taiwan had higher HR for LT compared with Eastern Taiwan. Highest income quartile neighborhood had higher HR compared with lowest income quartile neighborhoods (HR = 1.248, 95% CI = 1.055 – 1.478). People who had higher median income had significantly more LTs.

CONCLUSION

This study identified that the LT in Taiwan showed an increasing trend in the past years. People who were aged between 54-65 years old, male, lived in urban neighborhoods had higher prevalence rate. Fine and Gray’s competing risk model identified that people who lived in urban neighborhoods, Central Taiwan, highest income quartile neighborhoods and had higher income had more chance to liver transplantation. Further study should focus on the causal relationship between socioeconomic disparities and access to LT in Taiwan.

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