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Open Access Study protocol

Study Protocol - Accurate assessment of kidney function in Indigenous Australians: aims and methods of the eGFR Study

Louise J Maple-Brown12*, Paul D Lawton2, Jaquelyne T Hughes1, Suresh K Sharma1, Graham RD Jones3, Andrew G Ellis4, Wendy Hoy5, Alan Cass6, Richard J MacIsaac7, Ashim K Sinha8, Mark AB Thomas9, Leonard S Piers10, Leigh C Ward11, Katrina Drabsch1, Sianna Panagiotopoulos7, Robyn McDermott12, Kevin Warr9, Sajiv Cherian13, Alex Brown14, George Jerums7 and Kerin O'Dea12

Author affiliations

1 Menzies School of Health Research, Institute of Advanced Studies, Charles Darwin University, Darwin, Australia

2 Division of Medicine, Royal Darwin Hospital, Darwin, Australia

3 Chemical Pathology, St Vincent's Hospital, Sydney, Australia

4 University of Melbourne, Department of Medicine, Austin and Northern Health, Heidelberg, Victoria, Australia

5 Centre for Chronic Disease, The University of Queensland, Australia

6 The George Institute for International Health, University of Sydney, Sydney, Australia

7 Department of Endocrinology, Endocrine Centre Austin Health & University of Melbourne, Heidelberg Repatriation Hospital, Heidelberg West, Victoria, Australia

8 Endocrine and Diabetes Unit, Cairns Base Hospital, Queensland, Australia

9 Department of Nephrology, Royal Perth Hospital, Perth, Australia

10 Centre for Health and Society, School of Population Health, University of Melbourne, Melbourne, Australia

11 School of Chemistry and Molecular Biosciences, The University of Queensland, Australia

12 Sansom Institute for Health Research, UniSA, Adelaide, Australia

13 Department of Renal Medicine, Alice Springs Hospital, Alice Springs, Australia

14 Baker IDI Heart and Diabetes Institute, Alice Springs, Australia

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Citation and License

BMC Public Health 2010, 10:80  doi:10.1186/1471-2458-10-80

Published: 19 February 2010

Abstract

Background

There is an overwhelming burden of cardiovascular disease, type 2 diabetes and chronic kidney disease among Indigenous Australians. In this high risk population, it is vital that we are able to measure accurately kidney function. Glomerular filtration rate is the best overall marker of kidney function. However, differences in body build and body composition between Indigenous and non-Indigenous Australians suggest that creatinine-based estimates of glomerular filtration rate derived for European populations may not be appropriate for Indigenous Australians. The burden of kidney disease is borne disproportionately by Indigenous Australians in central and northern Australia, and there is significant heterogeneity in body build and composition within and amongst these groups. This heterogeneity might differentially affect the accuracy of estimation of glomerular filtration rate between different Indigenous groups. By assessing kidney function in Indigenous Australians from Northern Queensland, Northern Territory and Western Australia, we aim to determine a validated and practical measure of glomerular filtration rate suitable for use in all Indigenous Australians.

Methods/Design

A cross-sectional study of Indigenous Australian adults (target n = 600, 50% male) across 4 sites: Top End, Northern Territory; Central Australia; Far North Queensland and Western Australia. The reference measure of glomerular filtration rate was the plasma disappearance rate of iohexol over 4 hours. We will compare the accuracy of the following glomerular filtration rate measures with the reference measure: Modification of Diet in Renal Disease 4-variable formula, Chronic Kidney Disease Epidemiology Collaboration equation, Cockcroft-Gault formula and cystatin C- derived estimates. Detailed assessment of body build and composition was performed using anthropometric measurements, skinfold thicknesses, bioelectrical impedance and a sub-study used dual-energy X-ray absorptiometry. A questionnaire was performed for socio-economic status and medical history.

Discussion

We have successfully managed several operational challenges within this multi-centre complex clinical research project performed across remote North, Western and Central Australia. It seems unlikely that a single correction factor (similar to that for African-Americans) to the equation for estimated glomerular filtration rate will prove appropriate or practical for Indigenous Australians. However, it may be that a modification of the equation in Indigenous Australians would be to include a measure of fat-free mass.