Impact of Body Composition on the Accurate Assessment of Kidney Function in Indigenous Australians: the eGFR Study — ASN Events
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  3. Impact of Body Composition on the Accurate Assessment of Kidney Function in Indigenous Australians: the eGFR Study

Impact of Body Composition on the Accurate Assessment of Kidney Function in Indigenous Australians: the eGFR Study (#288)

Louise Maple-Brown 1 2 , Jaquelyne Hughes 1 2 , Leigh Ward 3 , Leonard S Piers 4 , G R Jones 5 6 , P Lawton 1 , A E Ellis 7 8 , R J MacIsaac 8 9 , A Cass 10 11 , W Hoy 12 , K O'Dea 13 , George Jerums 7 8
  1. Menzies School of Health Research, Charles Darwin University, Darwin, NT, Australia
  2. Division of Medicine, Royal Darwin Hospital, Darwin, NT, Australia
  3. School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
  4. School of Population Health, University of Melbourne, Melbourne, VIC, Australia
  5. SydPath, St Vincent's Hospital, Sydney, NSW, Australia
  6. University of NSW, Sydney, NSW, Australia
  7. Austin Health, Melbourne, VIC, Australia
  8. University of Melbourne, Melbourne, VIC, Australia
  9. Department of Endocrinology and Diabetes, St Vincent's Hospital, Melbourne, VIC, Australia
  10. The George Institute for Global Health, Sydney, NSW, Australia
  11. University of Sydney, Sydney, NSW, Australia
  12. University of Queensland, Brisbane, QLD, Australia
  13. University of South Australia, Adelaide, SA, Australia

Background: Differences in body composition raise the question that creatinine-based estimates of glomerular filtration rate (GFR) derived for use in European populations may not be appropriate for Indigenous Australians. The aim of this study was to assess if incorporation of fat-free mass (FFM) measurement improves performance of estimated measures of GFR (eGFR) in Indigenous Australians.

Methods: We measured GFR (mGFR) by plasma disappearance of iohexol over 4 hours and eGFR using 4-variable Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, without African-American correction factor, using enzymatic creatinine. Body composition was assessed by dual-energy X-ray absorptiometry in Darwin and Thursday Island. Participants were Indigenous Australians aged≥16 years.

Results: Indigenous Australians (n=135) were aged 47+15 years, 41% male, 40% with diabetes, 18% CKD stages 3-5, BMI 31+6 kg/m2, FFM 58+14 kg, mGFR 88ml/min/1.73m2. On multiple regression of mGFR, addition of FFM (beta-coefficient 0.005, p<0.001) to the model (including age, gender, creatinine) resulted in improved model performance (relative reduction root mean square error 5.3%). An equation was derived for eGFR using FFM (kg), creatinine (μmol/l), age(years), sex: FFM eGFR =4482 x Creatinine(-0.864) x (0.993)Age x (1.005)FFM x 0.823 if female.
Median bias (95% CI) = mGFR – eGFR, for each equation:

272-Louise.jpg

*p<0.05 compared to CKD-EPI

Conclusion: Addition of FFM to age, gender and creatinine significantly enhanced the model assessing GFR in Indigenous Australians. However, the FFM eGFR equation derived in this cohort demonstrated significantly improved performance to CKD-EPI eGFR only in obese males.