Diabetes rates for Indigenous Australians are three to four times that of the rest of the Australian population. And one of the resulting complications of diabetes is kidney disease.
Kidney function is assessed by estimating glomerular filtration rate (GFR) from serum creatinine levels. Despite widespread use to estimate GFR for Indigenous Australians the estimation formulas had not been tested in this population, until now.
Andrew Ellis at the Austin Clinical Pharmacology and Therapeutics Facility and the team at Austin Life Sciences have collaborated with members of the Menzies School of Health Research in Darwin and others on a large, three-year clinical trial. Known as the ‘eGFR Study’, it was undertaken across rural and remote areas of northern and western Australia including the Torres Strait islands.
“Different formulas exist for Caucasians and African-Americans when assessing kidney function by serum creatinine levels, but the appropriateness of such formulas had never been assessed in Indigenous Australians,” said Mr Ellis.
“We needed to compare the accuracy of the creatinine-based estimate of GFR against a reference method of measuring GFR.
“However, methods to accurately measure GFR that are routinely used in large hospitals (radio-isotope methods) are impractical or unavailable in remote areas. So to calculate the GFR we measured plasma clearance of Iohexol, (an inert marker of GFR) in more than 700 subjects using the slope-intercept method.
“The advantage is that samples can be collected from remote locations and sent for analysis in our facility. This obviates the need to rely upon the measurement of an isotope which has a short half-life and requires specialist on-site equipment” said Andrew.
Andrew’s facility has validated a new assay to measure Iohexol which provides an accurate way to measure kidney function that doesn’t require isotope or associated equipment handling in remote areas.
It is the first time this assay has been used in a clinical trial and Andrew’s facility is the only laboratory conducting this assay in Australia.
“Other formulas for estimated GFR were assessed and the study confirmed the appropriateness of the ‘CKD-EPI’ formula for estimation of GFR in Indigenous Australians. Further data on the effects of diabetes or of body build on the kidney health of Indigenous Australians will also soon be published.
“This provides a more accurate basis on which to evaluate kidney function the Indigenous population and will ultimately lead to better diagnosis and treatment outcomes,” said Andrew.