Improved estimation of glomerular filtration rate (GFR) by comparison of eGFR_{cystatin C} and eGFR_creatinine

Abstract

Objective. GFR-prediction equations based upon cystatin C and creatinine have better diagnostic performance in estimating GFR than equations based upon only one of the two markers. The present work concerns in what way a comparison between separate estimations of GFR based upon cystatin C (eGFR_{cystatin C}) or creatinine (eGFR_creatinine) can be used to evaluate the diagnostic performance of a combined cystatin C- and creatinine-based estimation of GFR. Methods. The difference between eGFR_{cystatin C} and eGFR_creatinine was compared with measured GFR (iohexol clearance) and a combined cystatin C- and creatinine-based estimation of GFR in a Swedish-Caucasian cohort of 857 adult patients. Results. A difference between eGFR_{cystatin C} and eGFR_creatinine of ≥ 40% indicated a markedly reduced diagnostic performance of the combined cystatin C- and creatinine-based estimation of GFR. Conclusion. Comparison of the agreement between eGFR_{cystatin C} and eGFR_creatinine can be used to evaluate the diagnostic performance of combined cystatin C- and creatinine-based estimations of GFR. If ‘threshold values’ for discordance are exceeded, it must be considered whether the clinical context requires the use of an invasive gold standard method to measure GFR. In some clinical contexts either creatinine or cystatin C are known to be invalidated as markers of GFR and in these situations the use of only the cystatin C- or the creatinine-based GFR estimate should be considered when the ‘threshold values’ are exceeded.

Key Words::

• Kidney function
• immunoassays
• kidney diseases
• cystatin C
• creatinine

Acknowledgements

The investigation was supported by grants from the Swedish Science Research Council (Project No. 5196) from the Alfred Österlund Foundation, Greta and Johan Kock Foundation, Medical Faculty of the University of Lund and from Region Skåne.

Declaration of interest: The authors have no conflicts of interest. The authors alone are responsible for the content and writing of the paper.