Inker et al reported an equation for estimated glomerular filtration rate based on serum creatinine and cystatin. Race is not included as a parameter. The authors are from multiple institutions in North America and Europe.
Patient selection: adult
Parameters:
(1) sex
(2) serum creatinine in mg/dL
(3) serum cystatin in mg/L
(4) age in years
Coefficient for the equation
(1) a1 coefficient for creatinine
(2) a2 coefficient for creatinine
(3) b1 coefficient for cystatin C
(4) b2 coefficient for cystatin C
(5) coefficient for age
(6) coefficient for sex
Parameter
Finding
Derived Value
a1
male
(MIN((serum creatinine)/0.9,1))^(-0.144)
female
(MIN((serum creatinine)/0.7,1))^(-0.219)
a2
male
(MAX((serum creatinine)/0.9,1))^(-0.544)
female
(MAX((serum creatinine)/0.7,1))^(-0.544)
b1
(MIN((serum cystatin)/0.8,1))^(-0.323)
b2
(MAX((serum cystatin)/0.8,1))^(-0.778)
value for age
0.9961^(age)
value for sex
male
1
female
0.963
eGFR in mL per min per 1.73 square meters =
= 135 * a1 * a2 * b1 * b2 * (age factor) * (sex factor)
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