Abstract
Chronic kidney disease had been identified worldwide as a non-communicable disease and a serious public health problem, being common, costly, and associated with increased morbidity and mortality. This is not only directly through the disease itself but also as an amplifier of other non-communicable diseases. This is more so for developing and low-middle-income countries. The common risk factors for its development amongst developing and low-middle-income countries has been identified as the common non-communicable diseases of diabetes and hypertension both of which are closely related to obesity. Samoa has identified non-communicable diseases as a critical issue for the health of the people of Samoa investing in a health strengthening project in collaboration with external donors that focuses on strengthening primary health care services with an emphasis on non-communicable diseases. However, chronic kidney disease is not included in the non-communicable diseases being targeted in this health system strengthening project.
Samoa is an independent Pacific Island nation that in 2005 invested in a haemodialysis service in response to a growing demand of kidney failure patients. Providing haemodialysis services in Samoa uses between five to eight percent of the health budget providing care to <0.1% of the Samoan population. These services are provided through the National Kidney Foundation of Samoa, a government state owned enterprise separate to the Ministry of Health.
In recent years, the National Kidney Foundation of Samoa has been concerned with the rapidly growing demand for haemodialysis and have focused on trying to understand this growing burden of kidney failure in Samoa. This has led to this thesis which has provided not only an opportunity to evaluate the organisations services but also an opportunity to have a clinical staff member trained in research skills as well. The National Kidney Foundation of Samoa however, recognised that the information currently available was likely to underestimate any calculations with poorly resourced infrastructure including health information systems. Recognising that since the opening of the local haemodialysis unit, many Samoans living in developed countries, like New Zealand, Australia, and the United States of America, were returning home to Samoa to continue their dialysis treatment, the National Kidney Foundation of Samoa looked for opportunities to compare the impact of chronic kidney disease in Samoa with other Samoan communities currently residing in developed countries where infrastructure is expected to be better than that in Samoa.
Samoa has a close relationship with New Zealand which has a large Samoan community particularly resident in the city of Auckland. Auckland is acknowledged as the largest Polynesian city in the world. Most Samoan individuals returning to Samoa for haemodialysis treatment have come from Auckland, New Zealand. Given the inter-relationship of these communities, this thesis explores the prevalence of chronic kidney disease and its associated risk factors in Samoa and amongst Samoans in Auckland, New Zealand, and associations between these identified risk factors and the development of chronic kidney disease in these two sample groups. The series of studies takes a pragmatic approach, given the varying existing datasets available for analysis from Samoa and New Zealand, to draw out a picture of what is happening in each community.
Since inception, the National Kidney Foundation of Samoa had never had an opportunity to evaluate its haemodialysis services and so the first aim was to evaluate the epidemiology of kidney failure in individuals who had received haemodialysis for kidney failure at the National Kidney Foundation. This study found that Samoa had a high kidney failure crude incidence rate of 223 per million population and a crude prevalence rate of 593 per million population. These figures are likely underestimated as they only evaluated individuals who had received or were receiving haemodialysis at the National Kidney Foundation of Samoa dialysis centre. Chronic kidney disease is recognised as the precursor to kidney failure with a long prodromal phase for which intervention can be implemented in early stages to slow and modify progression. The next study was to try to estimate the prevalence of chronic kidney disease in the community. To achieve this, several screening activities in Samoa delivered by the National Kidney Foundation as part of an expanded screening campaign were held over the month of March 2019. This second study evaluated fifteen screening events using point of care testing for serum creatinine and estimated glomerular filtration rate, urine dipstix analysis for proteinuria and haematuria, with a total of 1163 participants with a mean age of 50.5years and found an estimated chronic kidney disease prevalence of 44.5% [95% CI: 41.6, 47.4] and an age-standardised chronic kidney prevalence of 31.8%. This study also found a prevalence of the individual CKD stages of CKD 1: 3.7% [95% CI: 2.7, 4.9], CKD 2: 6.1% [95% CI: 4.8, 7.6], CKD 3: 30.7% [95% CI: 28.1, 33.4], CKD 4: 2.9% [95% CI: 2.0, 4.1], and CKD 5: 1.0% [95% CI: 0.5, 1.8]. The prevalences of the identified associated risk factors were obesity (BMI ≥ 32) 66.3% [95% CI: 63.5, 69.0], diabetes 30.8% [95% CI: 28.1, 33.5] and hypertension 54.3% [95% CI: 51.4, 57.2]. The third study looked to evaluate the prevalence of chronic kidney disease in the Samoan population resident in Auckland, New Zealand, by way of contrast to Samoans living in their homeland.
A sample from two Pacific Island health providers in areas of Auckland known to have large Pacific Island communities was obtained. The chronic kidney disease prevalence in this Samoan sample, determined from two or more chronic kidney tests (serum creatinine along with estimated glomerular filtration rates and/or urine albuminuria) more than three months apart, was found to be 17.8% with the total sample as the denominator rising to 36.3% when only those Samoans who had been tested was used as the denominator. The prevalences of the different CKD stages were CKD 1: 2.7% [95% CI: 2.4, 3.1], CKD 2: 4.9% [95% CI: 4.5, 5.5], CKD 3: 8.8% [95% CI: 8.2, 9.5], CKD 4: 0.7% [95% CI: 0.5, 0.8], and CKD 5: 0.6% [95% CI: 0.4,0.8] with the total sample as the denominator and CKD 1: 5.6[95% CI: 4.9, 6.4], CKD 2: 10.1% [95% CI: 9.1, 11.1], CKD 3: 18.1% [95% CI: 16.8, 19.3], CKD 4: 1.4% [95% CI; 1.0, 1.8] and CKD 5: 1.2% [95% CI: 0.9, 1.6]. The prevalence of the risk factors diabetes, obesity (BMI ≥ 32) and hypertension were 20.9%, 42.7% and 55.6% respectively.
This study has identified chronic kidney disease as an important burden for Samoan people both in Samoa and in Auckland, New Zealand. While chronic kidney disease is now recognised worldwide as an important public health problem and non-communicable disease, this needs to be emphasised in the Pacific region with education and support for Pacific Island nations like Samoa to integrate chronic kidney disease into national non-communicable disease policies and potentially into screening programmes.