Development and validation of GFR-estimating equations using diabetes, transplant and weight.
BACKGROUND
We have reported a new equation (CKD-EPI equation) that reduces bias and improves accuracy for GFR estimation compared to the MDRD study equation while using the same four basic predictor variables: creatinine, age, sex and race. Here, we describe the development and validation of this equation as well as other equations that incorporate diabetes, transplant and weight as additional predictor variables.


METHODS
Linear regression was used to relate log-measured GFR (mGFR) to sex, race, diabetes, transplant, weight, various transformations of creatinine and age with and without interactions. Equations were developed in a pooled database of 10 studies [2/3 (N = 5504) for development and 1/3 (N = 2750) for internal validation], and final model selection occurred in 16 additional studies [external validation (N = 3896)].


RESULTS
The mean mGFR was 68, 67 and 68 ml/min/ 1.73 m(2) in the development, internal validation and external validation datasets, respectively. In external validation, an equation that included a linear age term and spline terms in creatinine to account for a reduction in the magnitude of the slope at low serum creatinine values exhibited the best performance (bias = 2.5, RMSE = 0.250) among models using the four basic predictor variables. Addition of terms for diabetes and transplant did not improve performance. Equations with weight showed a small improvement in the subgroup with BMI <20 kg/m(2).


CONCLUSIONS
The CKD-EPI equation, based on creatinine, age, sex and race, has been validated and is more accurate than the MDRD study equation. The addition of weight, diabetes and transplant does not significantly improve equation performance.
Stevens
Lesley A
LA
Tufts Medical Center, Boston, MA, USA. lstevens1@tuftsmedicalcenter.org
Schmid
Christopher H
CH
Zhang
Yaping L
YL
Coresh
Josef
J
Manzi
Jane
J
Landis
Richard
R
Bakoush
Omran
O
Contreras
Gabriel
G
Genuth
Saul
S
Klintmalm
Goran B
GB
Poggio
Emilio
E
Rossing
Peter
P
Rule
Andrew D
AD
Weir
Matthew R
MR
Kusek
John
J
Greene
Tom
T
Levey
Andrew S
AS
D001835:Body Weight; D002908:Chronic Disease; D003404:Creatinine / Q000097:blood; D003920:Diabetes Mellitus / Q000503:physiopathology; D005260:Female; D005919:Glomerular Filtration Rate; D006801:Humans; D007674:Kidney Diseases / Q000097:blood / Q000175:diagnosis / Q000503:physiopathology; D016030:Kidney Transplantation; D008297:Male; D008433:Mathematics; D008875:Middle Aged
D003404:Creatinine