Impact of Ethnicity on Mortality 1- and 5-Years Post Kidney Transplantation in England Over the Last Decade

Abstract

Introduction: Disparities exist amongst minority ethnic groups in relation to both access and outcomes post kidney transplantation. However several limitations prohibit clear interpretation of these earlier studies due to confounders such as socioeconomic deprivation and universal health coverage. In addition, ethnicity demographics vary geographically and it is difficult to extrapolate data from other countries to the English population where south Asians constitute the largest minority ethnic group. Therefore the aim of this study was to assess the impact of ethnicity on mortality post kidney transplantation in England over the last decade. Methods: Data was obtained from Hospital Episode Statistics (HES), an administrative data warehouse containing admissions to all National Health Service hospitals in England. Data extraction was facilitated utilizing codes on procedural classification (Office of Population Censuses and Surveys Classification of Interventions and Procedures [OPCS-4]) and medical classification (ICD-10). We obtained data on all kidney transplant procedures performed in England between April 2001 and March 2010 with patient demographics obtained at time of transplant including age, sex, medical co-morbidities, social deprivation (Index of Multiple Deprivation 2007) and ethnicity. The primary outcome measure was mortality 1-year post kidney transplantation (HES data linked to Office for National Statistics to identify all mortality events), with 5-year mortality (for recipients between 2001-2006) the secondary outcome measure. Logistic regression algorithms were performed (R stats package) to identify independent factors associated with mortality (p < 0.05 considered significant). Results: Data analysis was performed on 15,218 kidney transplant procedures performed in England between 2001-2010 (adult and paediatric). Breakdown of patients by ethnicity were: white (72%, n=10,975), South Asian (8%, n=1265), black (5%, n=698), chinese (< 1%, n=58), mixed (1%, n=127), other (2%, n=273) and unknown (12%, n=1822). Modal age category for kidney transplant recipients based upon ethnicity was: white (age=41), south Asian (age=47), black (age=43), chinese (age=49), mixed (age=38) and other (age=39). There were 473 recorded deaths at 1-year post kidney transplantation for this study population. 1-year patient survival post kidney transplantation based upon ethnicity was: white (97.0%), south Asian (95.3%), black (97.0%), chinese (98.3%), mixed (99.2%) and other (97.8%). Logistic regression analysis identified ethnicity as an independent predictor for 1-year patient mortality (factored against age, sex, social deprivation and medical co-morbidities such as diabetes, cardiovascular or lung disease). Compared to south Asians (reference category), white recipients had decreased risk of mortality at 1-year post kidney transplant (OR 0.69, p=0.018). Black recipients also had decreased 1-year mortality but with borderline statistical significance (OR 0.64, p=0.098). The independent effect of ethnicity upon mortality after kidney transplantation was lost 5-years post-transplant. Conclusion: South Asians have greater risk of mortality at 1-year post kidney transplantation compared to white recipients and this effect is independent of age, socioeconomic deprivation and medical co-morbidities. However this difference is lost after 5-years post transplantation - therefore despite increased earlier mortality, long-term mortality data in England is comparable across different ethnicities. Factors influencing increased 1-year mortality amongst south Asians post-transplantation requires further investigation but likely represents increased cardiovascular disease burden.