Comparison of creatinine and cystatin C based eGFR in the estimation of glomerular filtration rate in Indigenous Australians: The eGFR Study

Elizabeth LM Barr, Louise J. Maple-Brown, Federica Barzi, Jaquelyne T. Hughes, George Jerums, Elif I. Ekinci, Andrew G. Ellis, Graham RD Jones, Paul D. Lawton, Cherian Sajiv, Sandawana W. Majoni, Alex Brown, Wendy E. Hoy, Kerin O'Dea, Alan Cass, Richard J. MacIsaac

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Abstract

Background The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation that combines creatinine and cystatin C is superior to equations that include either measure alone in estimating glomerular filtration rate (GFR). However, whether cystatin C can provide any additional benefits in estimating GFR for Indigenous Australians, a population at high risk of end-stage kidney disease (ESKD) is unknown. Methods Using a cross-sectional analysis from the eGFR Study of 654 Indigenous Australians at high risk of ESKD, eGFR was calculated using the CKD-EPI equations for serum creatinine (eGFRcr), cystatin C (eGFRcysC) and combined creatinine and cystatin C (eGFRcysC + cr). Reference GFR (mGFR) was determined using a non-isotopic iohexol plasma disappearance technique over 4 h. Performance of each equation to mGFR was assessed by calculating bias, % bias, precision and accuracy for the total population, and according to age, sex, kidney disease, diabetes, obesity and c-reactive protein. Results Data were available for 542 participants (38% men, mean [sd] age 45 [14] years). Bias was significantly greater for eGFRcysC (15.0 mL/min/1.73 m2; 95% CI 13.3–16.4, p < 0.001) and eGFRcysC + cr (10.3; 8.8–11.5, p < 0.001) compared to eGFRcr (5.4; 3.0–7.2). Accuracy was lower for eGFRcysC (80.3%; 76.7–83.5, p < 0.001) but not for eGFRcysC + cr (91.9; 89.3–94.0, p = 0.29) compared to eGFRcr (90.0; 87.2–92.4). Precision was comparable for all equations. The performance of eGFRcysC deteriorated across increasing levels of c-reactive protein. Conclusion Cystatin C based eGFR equations may not perform well in populations with high levels of chronic inflammation. CKD-EPI eGFR based on serum creatinine remains the preferred equation in Indigenous Australians.

Original languageEnglish
Pages (from-to)301-308
Number of pages8
JournalClinical Biochemistry
Volume50
Issue number6
DOIs
Publication statusPublished - Apr 2017

Keywords

  • CKD-EPI equation
  • Creatinine
  • Cystatin C
  • GFR
  • Indigenous

ASJC Scopus subject areas

  • Clinical Biochemistry

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