Chronic kidney disease: a large-scale population-based study of the effects of introducing the CKD-EPI formula for eGFR reporting

Abstract

Objective To evaluate the effects of introducing the Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) formula for estimated glomerular filtration rate (eGFR) reporting in the adult population in routine clinical practice with clinician-directed testing. Design Retrospective study of all creatinine measurements and calculation of eGFRs using Modification of Diet in Renal Disease (MDRD) and CKD-EPI formulae. Setting General population, Oxfordshire, UK. Participants An unselected population of around 660 000. Interventions Reporting of eGFRs using MDRD or CKD-EPI formulae. Primary and secondary outcome measures Evaluation of the effects of the CKD-EPI formula on the prevalence of different stages of chronic kidney disease (CKD). Results The CKD-EPI formula reduced the prevalence of CKD (stages 2-5) by 16.4% in patients tested in primary care. At the important stage 2-stage 3 cut-off, there was a relative reduction of 7.5% in the prevalence of CKD stages 3-5 from 15.7% to 14.5%. The CKD-EPI formula reduced the prevalence of CKD stages 3-5 in those aged <70 but increased it at ages >70. Above 70 years, the prevalence of stages 3-5 was similar with both equations for women (around 41.2%) but rose in men from 33.3% to 35.5%. CKD stages 4-5 rose by 15% due exclusively to increases in the over 70s, which could increase specialist referral rates. The CKD classification of 18.3% of all individuals who had a creatinine measurement was altered by a change from the MDRD to the CKD-EPI formula. In the UK population, the classification of up to 3 million patients could be altered, the prevalence of CKD could be reduced by up to 1.9 million and the prevalence of CKD stages 3-5 could fall by around 200 000. Conclusions Introduction of the CKD-EPI formula for eGFR reporting will reduce the prevalence of CKD in a primary care setting with current testing practice but will raise the prevalence in the over 70s age group. This has implications for clinical practice, healthcare policy and current prevalence-based funding arrangements.

Figure 1

Prevalence of different estimated glomerular filtration rates (eGFRs) with the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) formulae. The prevalence within the samples studied is indicated on the y-axis with eGFR on the x-axis. eGFRs were calculated using the MDRD formula (dashed line) or the CKD-EPI formula (continuous line). Overall, eGFRs calculated using the CKD-EPI formula are higher and better than those calculated using the MDRD formula.

Figure 2

Bland–Altman plot of the relationship between the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) estimates of glomerular filtration rate The x-axis indicates the average of the estimated glomerular filtration rates calculated using the MDRD and CKD-EPI formulae and the y-axis indicates the difference between these two estimates.

Figure 3

Graph of the prevalence of each stage of chronic kidney disease (CKD) within the samples tested grouped by age and gender. The y-axis indicates the percentage of the patients tested in each age group with estimated glomerular filtration rates in the ranges corresponding to the indicated CKD stages with each formula (M indicates MDRD, Modification of Diet in Renal Disease formula and C indicates CKD-EPI, Chronic Kidney Disease-Epidemiology Collaboration formula). Numbers on the x-axis indicate ages in years.

Figure 4

Changes at the estimated glomerular filtration rates (eGFR) cut-off boundary of 60 ml/min/1.73m² The x-axis represents patient groups divided according to age in 5-year groupings. The y-axis represents the percentage change in the number of people with an eGFR of <60 ml/min/1.73m² occurring with a change from the use of the MDRD (Modification of Diet in Renal Disease) formula to the CKD-EPI (Chronic Kidney Disease-Epidemiology Collaboration formula. The percentage change is negative if there is a reduction in the number of people with an eGFR <60 ml/min/1.73m².