Current equations estimating glomerular filtration rate in primary care: Comparison and determinants

Abstract

Objective. The aims of this study were to compare estimated glomerular filtration rate (eGFR) by Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equations, to assess the classification of chronic kidney disease (CKD) stages by both equations, and to identify factors associated with differences between both equations in patients with or at high risk of CKD managed in primary care. Material and methods. This was an observational study of 803 patients with CKD, long-standing, severe hypertension and diabetes exclusively managed in primary care. Bias and precision between the two equations used to calculate eGFR were quantified as proposed by Bland and Altman. Results. In 1534 eGFR calculations, mean eGFR_MDRD was 0.8 ± 3.6 ml/min/1.73 m² higher than eGFR_CKD-EPI. Precision between the two equations was ±7.1 ml/min/1.73 m². Classification of CKD stages by MDRD or CKD-EPI equations agreed in 93.3% of cases. Age above 70 years, eGFR below 60 and above 120 ml/min/1.73 m² were associated with higher eGFR_MDRD values; and age below 50 years and inadequately controlled hypertension with higher eGFR_CKD-EPI values. Conclusions. Comparison of eGFR calculated by MDRD and CKD-EPI equations demonstrated no clinically relevant difference. In addition, CKD classification by both equations agreed highly. As both equations performed equally well, the simpler and more established MDRD equation should be preferred in patients with or at high risk of CKD managed in primary care. Patients' characteristics seem to account for previously reported differences in the performance of CKD-EPI and MDRD equations.

Key Words::

• chronic kidney disease
• glomerular filtration rate
• MDRD equation
• primary care
• renal function

Acknowledgements

We gratefully acknowledge the excellent cooperation and support of all physicians and their staff in all participating practices. We also kindly thank Dr Anne-Maria Crichton for her critical review of our manuscript.

Declaration of interest: The authors declare no financial or other conflicts of interest. No funding was received.