A28(T)
HOW GOOD ARE THE MDRD AND CKD-EPI EQUATIONS AT ESTIMATING
GFR IN OLDER PEOPLE?
Kilbride, H1, Stevens, P1, Eaglestone, G1, Knight, S1, Delaney, M1, Farmer, C1,
O'Riordan, S1, Dalton, N3, Lamb, E2
1
Kent Kidney Care Centre, 2Clinical Biochemistry, East Kent University Hospitals
Foundation NHS Trust, Canterbury, 3Well Child Laboratory, St Thomas' Hospital,
London
PROBLEM: It is suggested that the MDRD study equation overestimates the prevalence of
lower GFR in older people. The new Chronic Kidney Disease Epidemiology Collaboration
(CKD-EPI) equation has been shown to reduce bias in comparison to the MDRD equation.
Neither equation has been extensively validated in older people.
AIM: To evaluate the relationship between measured and estimated GFR in older people.
DESIGN: Using difference plot analysis on log-transformed data we examined the
relationship between GFR measured by a reference iohexol method and estimated GFR from
the MDRD and CKD-EPI equations in people aged over 74 y. Subjects were asked to avoid
meat consumption prior to the test. Following a 5 mL bolus of Omnipaque 240 venous
samples were taken at 5, 120, 180 and 240 minutes post-injection. Iohexol and serum
creatinine were measured by istotope dilution mass spectrometry (IDMS). GFR was estimated
using the IDMS-related MDRD and CKD-EPI equations.
FINDINGS: To date 327 Caucasian subjects with a mean age of 80.9 4.8 y, M:F 0.98, have
been studied. Median iohexol GFR was 49.5 (IQR 7.2-96.3) mL/min/1.73 m . Performance
characteristics of the MDRD and CKD-EPI equations vs measured GFR are shown below:
Median (IQR) GFR, mL/min/1.73 m
% Bias (95%CI) all, n=247
% bias (95%CI) iohexol GFR <60, n=156
% bias (95%CI), iohexol GFR 60, n=91
Within 30% of iohexol GFR (all), n(%)
Within 30% of iohexol GFR (GFR<60), n(%)
Within 30% of iohexol GFR (GFR 60), n(%)
MDRD
51.8 (13.3-156.0)
3.0 (1.4 to 4.7)
2.5 (0.7 to 4.3)
3.5 (0.3 to 6.8)
197 (80)
114 (73)
83 (91)
CKD-EPI
50.8 (12.0-98.2)
0.9 (-0.5 to 2.3)
1.0 (-0.8 to 2.8)
0.8 (-1.5 to 3.1)
197 (80)
110 (71)
87 (96)
CONCLUSIONS: We found no evidence to support the contention that the MDRD equation
over diagnoses CKD in older people. Our data suggests that the CKD-EPI equation offers a
small improvement in accuracy over the MDRD equation in older people.