Implications of the CKD-EPI GFR estimation equation in clinical practice

Abstract

Background and objectives: Chronic kidney disease (CKD) is a significant public health problem whose diagnosis and staging relies upon GFR-estimating equations, including the new CKD-EPI equation. CKD-EPI demonstrated superior performance compared with the existing MDRD equation but has not been applied to a healthcare system.

Design, setting, participants, & measurements: We identified 53,759 patients with stages 3 to 5 CKD on the basis of either MDRD or CKD-EPI equations using two eGFR values <60 ml/min per 1.73 m² > 90 days apart from an outpatient setting. We compared patient characteristics, presence of related diagnosis codes, and time CKD classification between equations.

Results: The number of patients identified with CKD decreased 10% applying CKD-EPI versus MDRD. Changes varied substantially by patient characteristics including a 35% decrease among patients < 60 years and a 10% increase among patients > 90 years. Women, non-African Americans, nondiabetics, and obese patients were less likely to be classified on the basis of CKD-EPI. Time to CKD classification was significantly longer with CKD-EPI among younger patients. 14% of patients identified with CKD on the basis of either estimating equation also had a related ICD-9 diagnosis, ranging from 19% among patients < 60 years to 7% among patients > 90 years.

Conclusions: Consistent with findings in the general population, CKD-EPI resulted in substantial declines in equation-based CKD diagnoses in a large healthcare system. Further research is needed to determine whether widespread use of CKD-EPI with current guidelines could lead to delayed needed care among younger patients or excessive referrals among older patients.

Figure 1.

Age distribution of stage 3 to 5 CKD population on the basis of estimating equations. (A) Population classified with CKD by both CKD-EPI and MDRD (n = 46,985). (B) Population classified with CKD only by MDRD (n = 5951). (C) Population classified with CKD only by CKD-EPI (n = 823).

Figure 2.

(A) Time to classification of CKD by age on the basis of the MDRD equation. (B) Time to classification of CKD by age on the basis of the CKD-EPI equation. *Extrapolated time assuming a Weibull survival distribution.